Introduction
Geology is a young science when compared to the 'hard' sciences of mathematics, chemistry, and physics -- only a little more than 200 years old, beginning 'unofficially' with the writings of James Hutton, Scottish naturalist extraordinaire. Hutton is perhaps best known for his observation that "the present is the key to the past" -- or, uniformitarianism. Prior to Hutton's contributions, interpretations of the features and processes on the earth were founded in catastrophism. In the mid-1800s, Charles Lyell, British geologist, promoted the advancement of geology as science by his publications of Principles of Geology. Among the geologic principles presented in that writing include the law of superposition and principle of faunal succession.
The earth the other planetary bodies making up the solar system began with the contraction and heating of a solar nebula about 5 b.y. ago. The ages for all solar system bodies is ~4.65 b.y. By 4 b.y., the earth had differentiated into an Fe (+Ni) core, a mantle, and a crust. Continental crust is approximately 40-60 km thick, whereas the oceanic crust is much thinner, 6-10 km. The mantle extends from beneath the crust to a depth of ~2900 km -- so it comprises a very large part of the interior earth. The core has a large volume, also -- about the size of the Moon, for comparison. Much of the information about the compositions of the core and mantle come from the study of meteorites, the material (casually referred to as stones, stony irons, and irons) that falls to earth from space, and probably representing planetary material from the asteroidal belt, the moon, and from Mars.
Superimposed on the mantle and crust are the subdivisions of the earth identified as lithosphere, asthenosphere, and mesosphere. These 'zones', or 'layers', are the basis for plate tectonics, a model for the earth being comprised of a rigid outer layer, ~100 km thick, that is segmented into "plates" (with jigsaw puzzle-like outlines) that move slowly, about 2-14 cm/year, in various directions. Plates that move apart from one another are separated by divergent plate boundaries (also: spreading centers; mid-ocean ridges). Where plates meet, the boundaries are convergent and usually one plate (the oceanic one) is subducted beneath the other to create a subduction zone. The seafloors develop a trench at such convergent boundaries. Subduction zones are also marked by island arcs (in the ocean) and by continental margin mountain ranges -- like the Andes along western South America, or the Cascades in the Pacific Northwest. The third kind of plate boundary is where the plates simply slide by one another, most often called transform faults. I like to refer to them as boundaries marking plates sliding by one another.
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Mineralogy
Minerals are naturally occuring inorganic material with definite chemical and physical characteristics. These physical characteristics are manifested by the geometric forms that the bonded atoms create, such as a cube or a hexagonal prism. The chemical aspects of minerals depends on what elements are bonded together to create the geometric forms, such as oxygen, silicon, or iron. (check this page with a good definition/description)
Minerals are made of atoms -- which consist of protons, neutrons, and electrons -- that bond ionically or covalently. For ionic bonding, atoms transfer, or give up, an available electron to another atom with a vacancy for an electron; for covalent bonding, outer-shell electrons in neighboring atoms join, or overlap, to share in creating a single filled (with electrons) orbit (or shell). How do the terms ion, cation, and anion fit into this discussion about ionic bonding??
The number of protons identifies an element's atomic number. The sum of the protons and neutrons provides the mass number. Varieties of a particular element that have variable atomic weights due to variable amounts of neutrons are called isotopes. For our studies of geologic material, we only need to be familiar with the elements Si, O, Al, Fe, Mg, Ca, Na, and K.
Based on chemical compositions, there are many categories of minerals -- to name a few, there are pure elements, oxides, sulfides, carbonates, sulfates, and most important in terms of what makes up the earth's crust, the silicates (or rock-forming minerals). Silicates are comprised of a silica tetrahedron -- that is, a pyramoidal geometric form made of one Si atom surrounded (covalently bonded) by four oxygen atoms. Single tetrahedrons can comprise the physical and chemical structure of a silicate mineral (such as olivine), but tetrahedrons also combine in various arrangements to make chains, sheets, and frameworks. Of the silicate minerals to get acquainted with, there are the mafic ones, olivine, pyroxene (augite), amphibole (hornblende) , and biotite mica -- and then there are the felsic ones, such as quartz, feldspar, and muscovite mica. Remember, however, that feldspar includes plagioclase (Ca and Na variety) and orthoclase (K variety).
Minerals have physical properties that sometimes help you to discern among them. For example, hardness varies and can be expressed on a 1 to 10 scale (diamond at #10, the hardest; talc at #1, the softest). Other properties are luster, specific gravity (density), streak, and cleavage. Table salt, the mineral halite, is a good example of a mineral that cleaves in three directions -- all faces of its cubic structure.
Check out the carbon polymorphs!
Some summary comments about where and how minerals form: (1) crystallization from silicate melts (namely, magmas), as they cool from temperatures of about 1200 C; (2) from sea water, both hot (e.g., metal-bearing minerals, such as at hydrothermal vents) and cold (e.g., calcite; halite upon evaporation); and (3) from fresh water, such as quartz (and varieties thereof) precipitating from groundwater as it percolates through rock.
Sample questions:
1. A subduction zone marks
plate boundaries that are
a) mid-ocean ridges b) sliding part one another c)
converging d) diverging e) lithospheric
2. If two atoms have identical number of protons but different number of neutrons, they are
a) isotopes b) convergent c) bonded d) polymorphs e) conductive
3. A common type of meteorite that can be used to represent the central portion of the earth is
a) carbonaceous b) iron c) asthenospheric d) mafic e) mantle
Know these terms: lithosphere, asthenosphere, mesosphere, core, mantle, crust, divergent, convergent, spreading center, mid-ocean ridge, subduction zone, trench, transform fault, solar nebula, plates, catastrophism, uniformitarianism, meteorite
mineral, electron, neutron, proton, isotope, ion, cation, anion, ionic and covalent bondings, cleavage, luster, hardness, specific gravity, the names of the 'important' silicate minerals (e.g., plagioclase, olivine, biotite), silicon-oxygen tetrahedron, rock-forming minerals, ferromagnesian, polymorph, ion substitution
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Igneous Rocks
Igneous rocks -- those formed by the cooling and crystallization of silicate liquid, or magma, The magma has cooled either in an extrusive (on the surface) environment, such as during volcanism, or in an intrusive (inside the crust of the earth) environment that we call 'plutonic'. As you can imagine, magma cooling 'extrusively' will cool rapidly relative to cooling 'intrusively'. Depending on whether or not the cooling rate is fast or slow -- and also on the quantity of SiO2 and volatiles (like water) present in the magma -- different textures form in igneous rocks.
Igneous rock textures refer to the geometric relationships among grains and the shapes of the grains. Some general terms that we use for textures are aphanitic, phaneritic, and glassy. Aphanitic means that you can't see the individual grains with your eyes -- it is therefore fine-grained (aphanitic) -- and the magma likely cooled too rapidly for minerals grains to grow large. In phaneritic rocks, you can see the grains -- they are coarse-grained -- and the magma cooled slowly enough such that the minerals grew relatively large. A glassy rock cooled so quickly that mineral grains did not form at all and the magma became glass. This is often the case for volcanism, where magma (lava) cools rapidly and glass is part of the rock that forms instead of silicate minerals that would have crystallized under slower cooling conditions. (Note: glass is technically not a mineral because it is amorphous, or without organized crystal structure.)
Other textural terms include porphyritic, which refers to a rock with relatively large mineral grains in a fine-grained groundmass (or matrix). The large mineral grains of a porphyritic rock are called phenocrysts. Vesicular is another term. It refers to the presence of vesicles, holes in the rock that represent original gas bubbles; during volcanic eruptions and emplacement of lavas, the gas bubbles break and the gas escapes. Here's a site with good photographs of rock textures.
Plutonism, or intrusive magmatism, can create batholiths, stocks, dikes, and sills. So -- what are the distinctions?? -- both in size and geometry?? Batholiths are the largest of plutons, considered to have outcropping surfaces of at least 40 sq. miles, or 100 sq. km. Dikes are essentially vertical, or discordant, injections of magma into fractures, whereas sills are concordant (essentially horizontal).
The rock types you need to know can easily be grouped in terms of SiO2 and texture (fine vs coarse). I will leave the examination and learning of the rock classification chart up to you. But the names of the rocks are basalt, gabbro, andesite, diorite, rhyolite, granite, and peridotite.
How to form magmas in the first place ??
The process is called partial melting (of pre-existing rock). The can happen if (i) there is elevated heat, (ii) release of pressure, and (iii) addition of volatiles (e.g, H2O). A hotspot, like that represented by Hawaii, is a good example of elevated heat in the mantle. See the present-day location of the Hawaiian hotspot, called Loihi volcano (submarine). What are geologic examples of a hydrous environment and decompression (release of pressure) that can encourage partial melting of mantle rock??
One of the ways by which different rock types are created involves magma differentiation, or the process by which a body of magma segregates into different chemical zones. The importance of magma differentiation is that it produces various kinds of magma compositions (that is, the various rock types, once the magmas crystallize) by chemically 'evolving' the liquid that remains as crystallization procedes. Bowen's reaction series is an example of the progression of minerals that crystallize and magma cools -- the idea being that assemblages of different minerals create different rock types. Additionally, different rock types (magma types) can be produced by magmas mixing, or by magmas assimilating ('digesting') other rock types that they contact in the crust.
Special terms to
know from chapter 4
phenocryst, porphyritic, texture, aphanitic, phaneritic, glassy, partial melting, names of the major rock types (e.g., granite), batholith, pluton, stock, dike, sill
Example questions:
A 'reasonable' temperature for magma is
a) 5000oF b) 350oC c) 0oC d)
1200oC e) 32oF
The process that produces magmas
is
a) magma differentiation b) bonding c)
partial melting
d) polymerization e) crystallization
Rapidly crystallizing magmas will crystallize
a) phaneritic b) vesicles c) phenocrysts
d) fine-grained rocks e) geothermal gradients
end of material for Exam 1, May 28
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Volcanism can produce either lava flows -- magma that moves across the surface from a volcanic vent -- or pyroclastic material, produced during violent eruptions. Lavas, particularly basaltic in composition, are often ropey in appearance, or pahoehoe, or with an angular, jagged surface, called aa. (See the variety of lava flow types, including underwater 'pillow' lavas, at this site.) Pyroclastic material includes volcanic ash, usually angular particles of glass (quenched fragments of magma) <2 mm in size, and bigger fragments like bombs and blocks (bombs = clots of magmatic liquid cooled in the trajectory; blocks = pre-existing rocks included in the eruption). Pumice is part of the pyroclastic material, too -- refering to a porous (almost spongy-looking) material that represents the gaseous froth that occupied the top of a magma chamber before eruption. In fact, volcanic ash is often the fragments from bubble walls that broke during the volcanic eruption.
Whether or not an eruption is violent or 'quiet' depends to a large extent on the viscosity of the magma, which depends a lot on the abundance of SiO2 (silica) in the magma (temperature also influences viscosity). High SiO2 (rhyolitic) magmas are the most viscous and can retain gases to enable pressures to build up until the overlying rock can no longer contain the pressure -- the ultimate result is an explosive, pyroclastic eruption. Basaltic magmas, on the other hand, have lower SiO2 (and higher temperature) and therefore allow magmas to erupt in an essentially non-violent fashion.
Shield volcanoes are gently sloping and constructed from the more fluid basaltic magmas. Strato-composite volcanoes are steep-sided and produced from more viscous magmas, and they are generally made of layers of both lava and pyroclastic material (tuff and ash). Small volcanoes, generally only 100s of meters in diameter, are called cinder cones. They are often present on the flanks of shields and composite cones. What are the relative sizes of the volcanic types?? The volcanic particles, or pyroclastics, erupted include ash (generally <2 mm), blocks and bombs, and pumice (the magma "froth"). Consolidation of these particles make the volcanic rock called "tuff".
Now -- what is the connection with making magmas (by partial melting) and plate tectonics?? (Hints: subduction zones add volatiles to mantle, fascillitating melting; divergent plate boundaries relieve pressure on mantle rock).
How do volcanic island arcs (e.g., West Indies; Aleutian Is.) and continental volcanic mountain ranges (e.g., Cascades; Andes) fit into this relationship between partial melting and plate tectonics? What about relating a linear chain of volcanoes (e.g., Hawaiian Is.) to plate tectonics -- and in particular, to a mantle hotspot? Remember -- hotspots are "conduits" of heat in the upper mantle that cause continual partial melting and magma production.
Volcanism is neatly tied into plate tectonics, occurring at plate boundaries -- divergent and convergent. Island arcs and continental margin mountain (volcanic) ranges commonly form above subduction zones. Mid-ocean ridge systems are volcanic, forming at places of sea-floor spreading (divergence). Some volcanism occurs far from plate boundaries, such as Hawaii in the middle of the Pacific. This kind of intraplate volcanism is attributed to "hotspots" -- or conduits of heat in the upper mantle that continually produce magma to erupt -- as at Hawaii. As plate movement 'carries' away the volcanoes, a linear chain of volcanoes is created (like the Hawaiian 'chain')
Some summary remarks about volcanism and plate tectonics: There is a relationship between subduction zones and the occurrence of volcanoes -- namely, composite cones develop above subduction zones because the hyrdous environment of a subduction zone is conducive to partial melting to produce magmas. Magmas, less dense than solid mantle material, rise to occupy reservoirs in the crust. Occasional eruptions of those magma 'chambers' create volcanoes -- or where magma solidifies in the crust, plutons form. In an ocean environment, volcano island arcs form, such as the Aleutians, West Indies, and Japan. In a ocean/continent convergent plate boundary, continental mountains ranges develop, such as the Cascades and the Andes. The continental ranges are both volcanic and plutonic expressions of magma. Encircling the Pacific is the "ring of fire" -- a 'circle' of volcanoes formed above the ocean margins marking the subduction of the Pacific ocean crust (lithospheric plate).
Volcanism in intraplate regions are generally related to hotspots, or essentially fixed plumes of heat rising from deep levels in the mantle. As volcanoes form above a hotspot, such as at Hawaii, lithospheric plate movement gradually carries them away, a few centimeters/year, such that with long geologic time, a 'track' of volcanoes is created. The Hawaiian islands and related seamounts (plus the Emperor seamounts) are one such 'trace' of volcanoes stretching from the Hawaiian hotspot 1000s of km northwestward, such that ~70 m.y. of volcanism and plate movement are represented. On the continents, Yellowstone is a good representation of a hotspot. It, too, is the 'endpoint' of a trace of volcanism -- namely, the Snake River basalts and maybe event the Columbia River Plateau flood basalts.
Finally -- note that volcanoes generally have depressions at their summits. We call these craters, unless they are very large in diameter, such as >1 km. Then the term 'caldera' better applies. Crater Lake in Oregon is a good example of a really large collapse caldera formed after the eruptions of a strato-composite cone in the Cascades. The active Hawaiian volcanoes, Kilauea and Mauna Loa, have calderas at their summits.
viscosity, pyroclastic, bomb, block, ash, pumice, tuff, caldera, crater, volcanic island arcs, hotspot
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The two types of weathering are mechanical (also called physical) and chemical. The dominant process of mechanical weathering is frost wedging, whereby water freezing in pores and cracks exerts a pressure (wedging) upon freezing. If freezing and thawing occur repeatedly during a season, the cumulative wedging can be significant enough to cause rocks to fragment into smaller portions -- hence mechanical weathering. Accumulations of rock debris at the base of a cliff or slope are called talus slopes. Plant roots also cause wedging.
Another mechanical process is unloading (also called sheeting)-- the release of pressure on underlying rocks due to removal of overlying rock due to erosion. This "relief" of pressure enables rocks to expand, or "unload", and the result is fragmentation. Often, in granite bodies, the result of sheeting is to creat a domal shape, called exfoliation domes.
Chemical weathering is largely caused by dissolution, oxidation, and hydrolysis. Dissolution occurs when a weak acid, like carbonic acid, is produced from carbon and water and the acid contacts soluble rocks like limestone.
Oxidation is when oxygen combines with iron and an electron is stripped from the iron. The iron is oxidized and the original mineral structure is weakened. The resultant color is reddish-brown -- like metallic iron undergoing rusting (this, too, is oxidation). Mineralogically, ferromagnesian minerals (remember those??) are susceptible to oxidation.
Hydrolysis is a chemical process with a rather complex reaction formula. Mainly, what to know about hydrolysis is that the hydrogen ion from acid has the abililty to "attack" and break down the silicate structure -- making clay from silicates. Here a good fact to know!! Clay is a mineral -- actually it's a whole class of minerals (clay mineralogy is complex) -- and it's secondary in its origin. That means clay is produced as a by-product of weathering of "primary" minerals formed during crystallization of silicate melt (olivine, pyroxene, feldspars, etc. -- those are primary minerals).
So, what's your ideas about factors that control weathering rates??? Certainly you've thought of the importance of rock type (e.g., granite, with its 'tough' quartz, is resistant to chemical attack -- but it will fracture readily from frost wedging; limestone easily dissolves in "acid rain"). What about climate? -- and how can slope affect weatherng rates?? (the term 'slope' meaning topography), and the vegetation and the amounts of rainfall?
Here's an interesting result of combined mechanical and chemical weathering. Coarse-grained rocks like granite will often weather in sphere shapes -- spheroidal weathering. The reason is that corners of rock fragments offer the most surface area to be "attacked", and consequently wear away to become rounded -- giving the rock fragments a spheroidal appearance.
Soils are evaluated in terms of profiles. The profiles can be divided into horizons A, B, and C. Horizon A is at the top of a profile and contains the topsoil, organic material, and clay, but the clay has been leached of elements that are dissolvable by rainwater percolating downward through the horizon. In other words, Ca, Na, and K are likely to be depleted in horizon A, but Fe and Al somewhat enriched. Beneath, in horizon B, there is largely clay, but the horizon contains the precipitated material from horizon A -- so that Ca, for example, may be enriched here. Horizon C is the zone of transition into the bedrock undergoing the weathering to become soil -- so C contains 'boulders' mixed in part with small fragments of weathered rock (to create what might be called regolith; in contrast to soil, which by definition contains some organic material). Two common soil types in North America are pedalfer (in humid climates, eastern half of US) and pedocal (in drier portions; western half of US). How about laterite? They are highly enriched Fe and Al abundances?
oxidation, hydrolysis, solution (dissolution), leaching, talus slope, frost wedging, root wedging, exfoliation, sheeting, unloading, pedalfer, pedocal, laterite, horizons A, B, C, soil profile
1. A soil to be found in tropical regions that have unusually large amounts of precipitation is
a. lignite c. pedocal c. pedalfer d. laterite e. exfoliation
2. Clay is
a. a secondary mineral b. formed from magmas c. always a product of dissolution
d. related to 'hard' water e. in horizon C
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Look at detrital sediments (i.e., accumulated particles of broken rock) as relating to igneous rocks as sawdust relates to trees. Detrital sediments compact and cement to form sedimentary rocks that are named according to the sizes of the sediments comprising them. Conglomerate (and breccia) are comprised of the largest particles (boulder, pebble, and cobble sized), while sandstone, siltstone, and shale are comprised of particles from about 2 mm in size down to smaller 'dust'-sized material.
In general, detrital (or clastic) sedimentary rocks display layering, or bedding, because they originated in lakes, rivers, oceans, and sand dunes where particles were emplaced layer upon layer over long periods of geologic time. The rocks often retain those histories in their appearances. They are stratified, or layered ('strata' = root word - layers). The particles, whatever size, become compacted and maybe cemented together to form a coherent rock. The sediment particles are lithified, or transformed into solid rock. Some of the cementing agents are calcium carbonate (CaCO3), silica (SiO2), and iron oxide (FeO) -- also, very fine particles, namely clay, can bond larger particles together. The entire process of transforming unconsolidate sediments (that is, the particles) into a coherent sedimentary rock is called diagenesis (note: I didn't mention this term)
Chemical sedimentary rocks are products of precipitation of Ca, Mg, Fe, Si, P, Na, and CO3 from fresh water or marine environments. The precipitation can occur due to saturation of certain elements, such as in the formation of limestone, or minerals are 'forced' to precipitate by the evaporation of the water, such as when halite and gypsum form from shallow, evaporating seas. Often chemical sedimentary rocks have a "biologic" component, such as the shells of marine animals. We refer to these features that represent organic material as fossils. In one extreme case, the formation of coal, the sedimentary rock is 'all' biologic, or organic -- namely, vegetation that has evolved from life, to burial in a non-oxidizing environment, to reconstitution into peat, then lignite, and then finally to shiny, black, combustable rock that we call coal.
Some special features for clastic (detrital) sedimentary rocks.
- They have porosity. How do you determine the porosity of a rock?
- The particles can be sorted and rounded. How can these features originate?
- The particles are packed together in some arrangement and cemented.
Sedimentary structures
Sedimentary structures are features that remain in sedimentary rocks from the place and type of origin -- such as ripples that represent a river bottom or shoreline. Graded bedding refers to particle-size gradation, fine to coarse from top to bottom.
Sedimentary structures
Fossils are also parts of sedimentary rocks: These are organisms (long dead, of course) preserved in sedimentary rock. They are present because they were trapped in the burial and lithification process to make shales, limestones, and sandstones, and preserved -- usually by a chemical replacement process, such as calcium carbonate or silica replacing the original organic material. Fossils can represent formed animal and vegetation lifeforms, and they provide substantial information about the geologic environment in which the sedimentary rock formed and about evolutionary stages of lifeforms at that time. Check out the pix of a fossil that had to have been the neatest critter of the seafloor (extinct since about 300 m.y. ago) -- the trilobite. (and another!)
Remember, 'moving' laterally in a sedimentary rock formation represents a 'time line', or a constant time; laterally, there may be a facies change in the rock unit. On the other hand, examination of sedimentary rock units at one location represents, from bottom to top, a "column" of rock that represents a range in geologic time, from older (bottom) to younger.
Sediments and plate tectonics: remember that subduction zone trenches offshore from continental margins and island arcs serve as great site for collecting sediments. Burial, compaction, and lithification of trench sediments is one way by which we can relate plate tectonics to the formation of sedimentary rocks.
Some 'things' to think about:
1. What kinds of sedimentary rocks are likely to form in a trench that marks a subduction zone along the margin of a continent?
Oscillatory (symmetrical) ripple marks in a clayey-sandstone may represent _____________
A sedimentary rock formation that changes in facies from sandstone to shale to limestone may represent _____________ (what, in terms of varying geologic environments?).
A vertical column of rock (such as a road-cut exposure) may have sandstone at the base and shale at the top. Was this an environment of beach becoming shallow marine, or the reverse, where a shallow water marine environment receeded and a shoreline developed?
Some questions:
1. A well-sorted rock comprised of well-rounded particles suggests
a) very little transportation b) long transport c) low cementation
d) deep ocean environment e) breccias
2. What kind of sedimentary rock forms in the open ocean, far from land?
(and name is that rock if it contains substantial Mg?)
sediment, sizes of --> clay, silt, sand, gravel, pebble, cobble, names of the detrital rocks (including breccia), names of the chemical types of rocks (including evaporites), cross-bedding, packing, porosity, 'bedding', layering, stratified, facies, lithification
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Main types of metamorphism: regional and contact
(a minor type is cataclastic -- occurring locally in fault zones)]
The agents of metamorphism are: elevated temperature and pressure and active fluids, such as water
Results of metamorphism of 'parent' rocks include textural and mineralogical changes
Textural changes are best observed after the regional metamorphism of shale. For example, it become foliated -- meaning that there is orientation to the minerals or that there is layering. The metamorphic rock can acquire slaty cleavage, schistocity, and maybe gneissocity -- although this latter, gneissocity, may also result from metamorphism of coarse-grained igneous rock, such as granite. Foliation likely developes in a compressional stress field, such as during mountain building.
Rock types are slate, phyllite, schist, and gneiss -- which form a series that displays progressively larger mineral grain sizes due to increased recrystallization from being subjected to increasing grade of metamorphism
Some mineralogical changes may include the crystallization of new 'metamorphic' minerals, such as garnet, staurolite, and sillimanite (you don't have to memorize these mineral names). Because some of these metamorphic minerals represent origins in relatively narrow ranges of temperature and pressure, they can be used as index minerals that identify the temperatures and pressures at which metamorphism occurred (neat!)
So, what about metamorphic rocks that do not have foliation, such as marble and quartzite? They have granular textures, such as interlocking grains of CaCO3 making up marble and interlocking grains of quartz making up quartzite, and no particular orientation of mineral grains. Stress was not so important here, but rather, the elevated temperatures found in a contact metamorphic zone.
Think, then, about where metamorphism has taken place to create the metamorphic rocks of the crust. How about in the Appalachians, a mountain range that represents a geologic history of intense compressional stress. (mountain building = regional metamorphism = foliation). What about the non-foliated rocks?? They're probably from a contact 'aureole' around a magma emplacement, such as a batholith or stock, or even a thick dike.
Plate tectonics and metamorphism: check the illustrations in the textbook to see how plate tectonics equates with metamorphism. For example, convergent plate margins (and associated trenches) play a big role here. And also note that continental shields -- erosional remnants of ancient mountains ranges -- contain a preponderance of metamorphic rock.
A characteristic of metamorphic rocks that indicates an origin under 'stress' is
a) granularity b) index minerals c) foliation d) solifluction e) density
An index mineral, such as garnet, in a schist can help estimate
a) the kind of metamorphic process b) age of metamorphism
c) environment of metamorphism d) temperature and pressure of metamorphism
e) the rock type that underwent metamorphism
foliation, regional, contact, names of rock types with foliation, rock types without foliation, grade (of metamorphism), rock (slaty) cleavage, schistosity, gneissosity
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There is relative geologic time and absolute geologic time
As for relative time --> this means that the rock layers on the 'bottom' are older than the rock layers above. Simple -- right? This is what the Law of Superposition states. How about the Principle of Horizontality? It states that sediments are originally emplaced in a horizontal position.
So, when two sets of sedimentary rock layers are at angles to one another (lower set inclined; upper set horizontal) -- (you have to see a picture of such for this to make sense) -- a significant amount of time had to have passed between the formation of the lower set of rock layers (the inclined) and the formation of the upper horizontal set (namely, tilting occurred, followed by substantial erosion -- which correlates with much time). That arrangement between inclined and horizontal rock layers is called an angular unconformity. All of this addresses relative time in that we don't know the actual ages of the rock layers -- we just know that the lower rock layers have to be older than the upper (easy enough !!). Also check out other indicators of the passing of substantial amounts of geologic time: nonconformities and disconformities
Finally, what about relative times indicated by cross-cutting relationships? A rock unit, such as a dike, has to be younger than the rock formation it cuts across -- right ??
What's a particular location (famous tourist place) where you can see an angular unconformity, nonconformities, and disconformities all evident within a small geographic area?
Relating the outcroppings of rock formation across geographic areas (that is, in a horizontal direction) is correlating the different rock formations. If rock formations correlate, then they are of the same age and characteristics. What are the characteristics to consider? Well, remember that there's texture, color, grain sizes, fossil content, any fabric features, such as layering, and sedimentary structures, such as cross-bedding.
For Absolute time, you need to know about radioactivity -- the spontaneous breakdown of the nuclei of some isotopes, such as U-238, or Rb-87. By understanding the details of the radioactive decay of certain isotopes, geologists (or geochronologists, actually) can establish the actual age of formation of an igneous rock (formation).
One way of looking at this is to consider half-life, or the amount of time it takes for a 'batch' of atoms representing a 'parent' radioactive isotope to decay (diminish) to one-half in number -- meaning that the 'daughter' isotope and the parent isotope are present in equal number of atoms within a 'closed' environment, such as a mineral grain in a volcanic rock. By knowing the decay constant and therefore the half-life of the parent isotope, the age can be determined (in this example, the age, or the time since origin of the mineral grain in the volcanic rock) as equal to the half-life -- whatever value that is, like maybe 1.4 b.y.
So, what is the age if three (3) half-lives have passed??
Remember, too, that types of radioactive decay include alpha decay, beta emission, and electron capture. And that geologists commonly use the relationships between parent isotopes K-40, Rb-87, and U-238 and their respective daughter isotopes Ar-40, Sr-87, and Pb-206. Respective half-lives for these isotopes are about 1.3 b.y., 47 b.y., and 4.5 b.y.
Now -- thinking of U decaying to Pb -- how does radon fit into this 'program'???
Carbon-14 dating is interesting -- not so much for geology, but usually for anthropological reasons. Its half-life is about 5730 years -- not very long -- so when it is applied to geology, such as dating dead organic material associated with glaciation (i.e., glaciers move through forests, killing trees), C-14 dating can only 'reach' back to a few tens of thousands of years.
Finally -- be knowledgable of the Geologic Time Scale, and become familiar with these times within the time scale: Precambrian, Paleozoic, Mesozoic (Triassic, Jurassic, Cretaceous), Cenozoic (Tertiary; Pleistocene). What are some significant life-evolution events to associate with these times? What is the length of time represented by the Mesozoic? When did dinosaurs live? When did humans come on the 'scene'?
Good to know:
correlation, absolute and relative geologic times, angular unconformity, nonconformity, disconformity, radioactivity, isotope, half-life, various units of the geologic time scale
1) If we equated the geologic time scale to
a 24-hour day, existance of human life (assume humans have existed
about 2 millions years) would be the equivalent of
a. one hour b.
one second c. one week d.
one day e. 45 seconds
2) What rock type is used for radioactive dating?
a) sedimentary b) igneous c) limestone d) coal e) carboniferous
3) If a mineral contained 25 atoms of a parent isotope and 75 atoms of the daughter isotope, and if the decay half-life
is 3.5 m.y., how old is the mineral?
a. 3.5 m.y. b. 1.75 m.y. c. 7 m.y. d. 14 m.y. e. 3 m.y.
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Rock Deformation (structural geology)
Rock behaves in elastic, plastic, and brittle fashion when subjected to stress. Compressional stress and plastic behavior will yield anticlines and synclines; compressional, tensional, and shear stresses applied to the point of brittle behavior within rock formations will produce reverse, normal, and strike-slip faults, respectively.
Anticlines are folds that have the oldest rock formation(s) in the core (center), and synclines are folds that have the youngest rock formation(s) in the core. These folds can be symmetrical, asymmetrical, or overturned. The limbs of anticlines and synclines have 'strikes' and 'dips', which specify orientations in a particular directions. Additionally, anticlines and synclines have a plunging aspects, whereby the crests and troughs plunge, or 'disappear', into the crust at a particular angle relative to horizontal.
Reverse faults demonstrate relative upward movement of the hanging wall, whereas normal faults demonstrate the opposite. (so -- what's a hanging wall?) If it is certain that the hanging wall of a reverse fault was thrust up (as opposed to the possibility that the footwall moved down), then it is proper to call the reverse fault a 'thrust' fault. Strike-slip faults demonstrate lateral movement, in either a right-lateral or left lateral direction. What is a well-known strike-slip fault? And how do strike-slip faults relate to transform faults?
What are horsts and grabens, and where can you find them? What kinds of faulting do there represent?
Folded rock layers can be illustrated in two dimensions (maps) by using strike and dip symbols. Dip refers to the direction and inclination a rock formation is 'dipping', and strike direction (perpendicular to dip direction) specifies the orientation of the rock formation with respect to north (magnetic).
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anticline, syncline, 3 types of faults, hanging wall, footwall, thrust, strike and dip, plunge, plastic, brittle, elastic
1) If two limbs of a fold were dipping toward one another at 20 degree angles, this would be
a) a normal fault b) a strike-slip c) an anticline d) a syncline e) a strike
2) If a rock layer is dipping 20 degrees to the northwest, what is its strike??
a) N45oE b) N-S c) N45oW d) N20oW e) N20oE
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Earthquakes (and earth's interior)
Earthquakes are vibrations produced in the earth by rapid release of energy. The place on earth above the source of the energy is the epicenter, whereas the actual site of energy release is the focus. Earthquakes are caused by movements along faults, and the energy is transmitted, or propagated, as seismic waves.
Some seismic waves propagate like sound waves -- these are primary, or P waves; another kind of seismic wave travels like light waves (in sine wave fashion) -- these are secondary, or S, waves. Both P and S waves are body waves, because they move through the body of the earth. Typical wave velocities near the surface of the earth (in the crust) are P = ~ 7-8 km/sec and S = ~ 3.5-4 km/sec.
There are also long waves, or L, which move along the surface like ripples in a pond. These L waves cause most of the earthquake damage in society.
Seismology is the study of earthquakes, and seismographs (sometimes called seismometers) are the instruments that measure and record earthquakes. See diagrams in your book for understanding how seismographs work.
Earthquake focii and epicenters are most often associated with plate boundaries -- where the subduction zones (Benioff zones) produce the most intense and deepest earthquakes. Divergent boundaries yield the least intense. Strike-slip faults (transform faults), like the San Andreas fault, can produce intense, but not necessarily deep, earthquakes.
We most often measure earthquake 'strength' in terms of Richter scale magnitude, a measure of wave amplitude recorded on a 1 to 10 log scale. Each Richter scale reading increase of "1" therefore corresponds to 10 times greater wave-amplitude magnitude than the previous number on the scale. The actual energy, in terms of ergs, increases ~32 times for each number increase on the scale.
Destruction from earthquakes depends of several variables: the intensity of the earthquake, the foundation (e.g., solid rock vs. clay-rich foundation that may undergo liquefaction); whether or not fires or landslides (mass wasting) start; whether or not a tsunami is generated (what's a tsunami??)
So, can E-Qs be predicted?? Not really, in the sense of 'pinning' down a time. But there are clues to be gathered about the possibility of whether or not an earthquake is imminent. For example, animal behavior (responding to the 'building up' of crustal stresses) and radon gas increases in well-water are useful. Lasar applications, tiltmeters, and strainmeters also measure gradual changes in the crust. And seismic gaps and seismic probability can help isolate an area next 'on the list' to experience an earthquake. Psychics and mystics haven't been too helpful and generally cause 'panic' in the population. Check out this 'prediction' by animals website
Exploration geologists/geophysicists create seismic-wave energy by shooting dynamite charges or by using air-guns towed from ships to send seismic waves into the subsurface or sea bottom. The waves reflect from the various layers of rock and sediment to create a 'picture' of the subsurface geology. The objective is to use the subsurface images to determine whether oil or gas are present in the crustal rocks of a particular area.
Earth's Interior
The earth has shadow zones with respect to where body seismic waves from a certain epicenter/focus will be recorded. These so-called shadow zones are related to P waves traveling like sound waves and S waves propagating like light waves. Note from diagrams in the book how the regions (in terms of a 360-degree circle/sphere) of these shadow zones differ.
The density of the medium that propagates seismic waves determines the velocity of the waves -- namely, the denser, the greater the velocity. This relationship helped determine early investigators that there was a Moho -- an interface between upper-level crustal rock and underlying mantle rock. The Moho is shallower beneath ocean crust than beneath continental crust. Seismic wave propagation also helped determine the presence of the details for the core of the earth, and helped to recognize that there was a 'low-velocity' zone in the upper mantle.
Know: body and surface (seismic) waves, P and S waves, surface waves (called L waves, for 'long'), shadow zones, Benioff zone, Moho, epicenter, focus, Richter scale, seismograph, tsunami, core (inner, outer), mantle, crust, earthquake, magnetic field, low-velocity zone, lithosphere, asthenosphere.
End of material for Exam 3
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This topic addresses movements of large portion of 'real estate' under the influence of gravity. It is not erosion, in the sense that there is no transporting medium such as water or wind. Some reasons that certain areas are mass wasted has to do with water weakening the coherency of the geologic material and bogging it down with excess weight, lack of vegetation, and earthquake triggering. The types of rock that make up a slope are influencial, too -- some making for a more coherent foundation than others.
We can classify the mass wasting processes by:
Type of material: soil, regolith, debris, mud, earth, rock
Type of motion: fall (this makes talus), slide (including slump), flow (as a viscous fluid)
Rate of movement: ranging from really fast, avalanche-speed, to snaily speeds (much less, actually), such as creep
We can give the mass wasting processes particular names:
Slump (implying a curved sliding plane), slide (implying a well-defined sliding plane), rockslide, debris flow (usually channelized flows, like mudflow), earth flow, creep, and solifluction. We usually don't use that general name, 'landslide'. Where does 'lahar' fit into this topic??
What can you say about permafrost and where in the world can you find some ???
How do you identify creep occurring in an urban environment? (be polite)
rock fall, debris fall, rock slide, debris slide, slumping (slump block; rotational), talus, solifluction, permafrost, debris flow, mudflow, creep, regolith, lahar
Sample questions:
1) A debris slide or mudflow associated with abundant volcanic material is a(n)
a. talus b. lahar c. rock avalanche d. liquefaction e. solifluction
2) Permafrost is most closely related to what
kind of mass wasting?
a. debris avalanche b. solifluction
c. talus d. debris flow e.
mudflow
3) When rain saturates hillsides in southern California each March-April, what kind of mass wasting occurs?
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The hydrologic cycle addresses the paths that water takes on, above, and beneath the surface. For example, water evaporates from the oceans, moves over land as clouds and precipitates as rain and snow. That precipitation can enter the subsurface as groundwater, run off into streams to be carried back to sea, become 'locked up' as glacial ice, or be taken in by plants and transpired back into the atmosphere.
Channelized water -- streams, rivers -- generally moves laminarly or turbulently, depending on velocity and stream channel roughness. This can be considered a particular characteristic of a stream.
Streams have other characteristics such as gradients, cross-sectional shapes, and discharge. Gradient measures the slope over a particular distance, the cross-section evaluates wide-shallow, deep-narrow, or U-shapes of stream channels. The discharge measures the volume of water that passes a certain point over a unit of time. Note that gradient over a long distance is the longitudinal profile of a stream.
A stream can only erode as deep as the elevation of the body of water it empties into, a lake or the ocean. This creates local and ultimate base levels. A stream could be either eroding its channel or depositing sediment onto its bed. [not discussed: Streams that are neither eroding or depositing are "graded", and, they can develope meandering paths.] A stream erodes by abrasion (using particles in its load), by dissolution, by plucking up particles, and simply by the impact of the water on rock, such as beneath a water fall.
Stream loads are classified as bed loads, suspended loads, and dissolved loads. Bed load particles are pushed or rolled along the bottom, or move by saltation, the hopping and skipping caused by impacting particles in motion.
Know: gradient, discharge, load (3 types), longitudinal profile, base level, abrasion, saltation
1) The longitudinal
profile of a stream shows that it is steepest
a) in the middle b) in the headlands c)
at the delta d) at the mouth
e) along the floodplain
The maximum load a stream can carry is a measure of its capacity, where the largest size particle it can carry is competence. These characteristics can change seasonably with the rise and fall of water level, velocity, and volume.
Some special characteristics are braided channels (choked with sediments such that 'bars' form) and meandering channels. The outside of the meander -- with highest velocity -- erodes, or creates a cut bank, and the inside of the meander deposits and creates a point bar. Meandering streams are usually found on floodplains, where natural levees can occupy the banks and separate the stream from the floodplain. During flooding, a stream may "short circuit" a meander, and upon receding back into its channel, continue to use the 'short circuit route' and not the meander. The isolated, or 'cut off', meander becomes an oxbow lake. (about to become an ox-bow lake).
Where a stream empties into a body of water, usually a delta of sediment is constructed due to the loss of carrying ability and 'dropping' of the load. As the river moves across this newly constructed 'real estate', it breaks up into smaller streams, or distributaries. In the case of a mountain stream 'emptying' out of the mountains onto a valley floor, the drop in velocity (and hence, the carrying capacity) leads to construction of an alluvial fan. What exactly is alluvium?
Floodplains are the regions along rivers and streams that are susceptible to flooding. After many floods, accumulations of relatively coarse sediments build up along river banks from the flood-water sediments 'dropped' by receding flood waters. These 'walls' of sediment lining the river are natural levees. They separate the river from its floodplain.
Within a particular region or drainage basin, stream channels will create a particular pattern, such as dendritic, rectangular, trellis, or radial. Exactly what kind developed depends on the structure and composition of the underlying rock. For example, flat-lying rock will generally lead to dendritic, while folded rock formations that undergo differential erosion will create trellis patterns. Fracture patterns in rock will often lead to rectangular patterns, and volcanoes develop radial. Drainage basins are separated by 'highs', or divides, with rain water flowing down one side or the other side of a divide.
The evolution of stream valleys: Stream valleys can be V-shaped, usually in their mountain sources, and the channels are considered 'young'. Wide channels with meanders and moving across floodplains are indications of 'mature' streams.
Know these: floodplain, levee, delta, alluvial fan, meander, braided, point bar, cut bank, oxbow lake, drainage patterns (4 types), divide, distributary
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Beneath the surface is a "water table" -- the interface between a zone of water-saturated geologic material (rock, soil) and the overlying zone of aeration, or geologic material that does not contain permanent water.
For groundwater in the 'zone of saturation' to be usuable by extraction and consumption, the medium containing the water must be both porous and permeable -- creating an aquifer. If the rock or soil containing the groundwater is porous but not permeable, it will not enable water to move through it and therefore it creates an aquitard.
Water in an aquifer moves very slowly, like only centimeters a day. Darcy's Law states that groundwater moves at a velocity that is proportional to the gradient of the water table. Because it moves so slowly, groundwater cannot replenish a portion of an aquifer from which water is continually extracted, such as by a well established for water consumption. The result is a 'depressed' water table in the vicinity of the well bottom, or a cone of depression.
Some water tables are local, and create perched water tables. These are often responsible for springs that seep water along a valley wall or above a stream bank. In rare cases, the replenishment zone for a laterally extensive aquifer is high in the mountains, creating a hydraulic 'head' on the groundwater in the same aquifer at locations much lower in elevation. This 'head', or water pressure, can create an artesian spring or well.
Groundwater can dissolve limestone and create caves and caverns. Drippings of CaCO3-rich groundwater from the roofs of caverns precipitates columns of CaCO3 called stalactites and stalagmites. Karst topography, or sink holes, also results from dissolution of limestone. On the other hand, if groundwater becomes heated by a magma reservoir in the crust, it will become superheated and 'erupt' at the surface as a geyser -- and can sometimes be used to generate power.
water table, aquifer, aquitard, perched water table, cone of depression, porous, permeability, artesian, spring, karst, stalactite, stalagmite, geyser, groundwater
Sample questions
1) Gasoline leaking from a storage tank will pass downward through the zone of aeration to the water table and
a) mix with the groundwater b) remain approx. at the water table c) sink to the bottom of the aquifer
d) rise back up to the surface e) create a cone of depression
2) A cone of
depression results from
a) perched water tables b) artesian springs
c) permeability
d) consumption e) aquifer contamination
3) At the outer banks, extraction of fresh groundwater can lead to (see Fig. 11.18 in textbook)
a) groundwater becoming replenished b) contamination by industry c) sea water encroaching from beneath the available fresh water d) springs e) perched water tables
4) Clay-rich rock (e.g., shale) can serve as an aquifer if it is
a) gray b) faulted c) folded d) highly fractured e) perched
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Glaciers and glaciation
Above the snowline, accumulations of snow can become 'metamorphosed' to firn and ice to form glaciers. In mountainous regions, valley (alpine) glaciers move through valleys and transform them into U-shaped valleys -- and during their descent, they create and/or develop ground, lateral, medial, and terminal moraines. Moraines are comprised of highly unsorted material (various sizes), and as a soil-type, this is called till.
Large accumulations of ice, such as on Antarctica and Greenland, are ice sheets or continental glaciers. Unconfined by walls, the only moraines that develop are ground and terminal.
Glacial ice moves internally and on its base, but very slowly -- maybe only a meter to several meters a day (on average). As they move over irregular surfaces, fractures at the top occur due to the brittle ice accommodating the 'flexing'. These surface fractures are crevasses. At the base of a glacier, the ice transports rock fragments of various sizes, boulders to 'dust'-sized material. Depending on size, this bottom material will gouge, scrap, groove, or polish the floor over which the ice moves. Valley glaciers sculpt their host mountains to shapes that creates the geologic features called cirques , horns, and aretes. The cirque is the bowl-shaped depression in which valley glaciers originate. Glaciated mountains will also have hanging valleys. How do these valleys originate? And cirques will fill in with water, once the glacier is gone -- this creates lakes called tarns.
At the foot, or end, of a glacier -- whether a valley glacier or a continental ice sheet -- meltwater carries away fine sediments from the ground moraine to create an outwash plain of rather well-sorted material. Any ice that becomes isolated on the outwash plain and melts leaves a 'kettle' that will fill in with water to form a lake. What are some U.S. states that have kettles??
The many ice ages that occurred in Cenozoic time were during times of global cooling -- which have been attributed to variations in the physical relationships between the earth and sun. For example, there are cycles of orbital eccentricity (about 100,000 years), axial tilt (about 41,000 years) and axial wobble (about 22,000 years), that, when coinciding, can affect the amount of sun's radiation that reaches the earth's surface. The less radiation, the cooler the climate -- and the possibility of more of the earth's H2O that we observe today occurring as ice. What names are associated with recognizing and explaining ice ages? Sea level was lower during the ice ages because such large volumes of water were tied up as ice. Afterwards, with climate warming to melt the continental ice sheets, sealevel rose. Any U-shape glacial valleys at the shorelines (of the lowered seas) were innudated and became fjords (drowned glacial valleys). Often, the continental glaciers carried with them and later 'dumped' boulders from afar -- which, being out of place, are "erratic" boulders.
moraine (4 types), till, crevasse, firn, snowline, cirque, horn, arete, tarn, kettle, hanging valley, fjord, outwash plain, erratic (rocks), causes of ice ages
1) If you were boating in a tarn, you would likely be
a) along a shoreline b) near the 'foot' of a glacier c) in glaciated terraine d) on an outwash plain e) below the water table
2) Crevasses develop because
a) the ice behaves as rigid material b) because the glacier
moves below the snowline c) the ice
slides on it base
d) the ice is forming moraines
e) till is unsorted material
3) Which countries are known for having many fjords??
4) Why are tills accumulations of material representing a wide range of sizes??
End of material for the Final, Exam 4, June 20
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Some historical aspects of Plate Tectonics
Alfred Wegener is credited with the first 'version' of plate tectonics: continental drift. He envisioned Pangaea, a supercontinent (comprised of Gondwanaland and Laurasia), as breaking apart and the continents floating away from one another like icebergs floating in water. Wegener's model for continental drift was 'dormant' until about the mid-'60s when magnetic properties of ocean crust were measured. These 'magnetic stripes', as they're called, indicated that various regions of the seafloor are spreading apart.
Today we know that the seafloor spreads away from mid-ocean ridge systems (volcanic mountain ranges on the seafloor) and that ocean floor disappears into subduction zones. The subduction zones were first identified as that which were called Benioff seismic zones, or seismic planes along which deeper earthquakes occur at deeper levels beneath an island arc (e.g., Aleutians; West Indies) or continental mountain ranges (e.g., Andes). Ocean crust moves from the various spreading centers at rates of 3 - 17 cm/year. So, ocean crust is much younger than typical continental crust -- generally not older than 250 m.y.
The North Atlantic ocean floor began to form with the breakup of Laurasia about 200 m.y. ago, and the South Atlantic began to open with the breaking of Gondwana about 135 m.y. ago. About how old is the ocean floor offshore from North Carolina??
There was an Atlantic Ocean before the one we know today -- a proto-Atlantic. It closed about 500 m.y. ago and gradually folded the eastern margin of proto-North America (by compression stresses) to create the Appalachian Mts. over the following 100 m.y. or so. This closing of the proto-Atlantic formed Pangaea -- which was 'stable' until about 200 m.y. ago. During the formation of the Appalachians, thrust faulting occurred in North Carolina, some of which can be seen in the Grandfather Mt. area.
Know these:
Wegener, magnetic stripes, plate boundaries (all types), hot spots, Pangaea,
Laurasia, Gondwana
Waves approaching a shoreline will refract, or bend -- because they most often approach at angles to the shoreline (rather than perfectly parallel) and the part of the waves closest to the shoreline begins to 'drag'. One of the results of waves approaching at angles to beach fronts is the creation of longshore currents. These 'currents' move particles along the beach -- beach drift, or longshore drift -- in a 'zig-zag' path. This happens because particles are pushed up the beach front normal to the breaking wave crest, and then the particles roll down the beach face perpendicular to the shoreline.
Beach drift creates spits and baymouth bars,. Offshore, wave energy creates barriers islands by piling up sand. The barriers can migrate and become diminished from wave energy imparted on them over lengths of time. At the rocky shorelines, wave energy erodes by abrasion and by its hydraulic impact. In the process, wave-cut cliffs and platforms form, and remnants of coast are left 'behind' as stacks, or seastacks -- some of which develop arches.
Offshore islands are sometimes created by wave action. The Outer Banks are examples of such islands. Actually, they may represent other processes -- such as, inundation of giant (and ancient) spits or beach dunes due to rising sea level associated with waning ice ages.
Due to sea level changes over periods of geologic time, some river valleys have become 'drowned' to create estuaries. What are some states that have estuaries??
Society attempts to retard beach erosion, or reduce beach drift in the longshore current, by constructing groins and jetties ('walls') essentially perpendicular to the shoreline. In what specific shoreline environment will be jetties be constructed? What about breakwaters? How do these features differ from groins and jetties -- and what long-term effects can they have on the beach front?
Tides are the daily risings and fallings of water at the shoreline. The moon's gravity is the cause, but the sun's gravitational pull is also a factor. How do these two celestial bodies fit into creating the types of tides called spring and neap??
spit, baymouth bar, refraction, longshore current, beach drift, sea stack, estuary, groin, jetty, breakwater, types of tides (and causes)
1) If you walked on a curved sand bar extending into a bay, you would have been on a(n)
a) breakwater b) barge c) jetty d) spit e) estuary
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Check out Rodinia in this assemblage of plate reconstructions
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That's it !!
Note -- if you want to another geology course, such as to fullfill a science requirement: take Historical Geology, MEA 102, taught each spring by Dr. Lonnie Liethold (she does a great job; the class is usually 25 to 30 students). There is a lab with the course.
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