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Geology: Test 2
| Question | Answer |
|---|---|
| What are the two kinds of weathering? Name and describe them. | Mechanical weathering breaks down a mineral or rock into smaller pieces but doesn’t change it chemically (disintegration). Chemical weathering changes rocks and mineral chemically (decomposition). |
| How does mechanical weathering pave the way for chemical weathering? | Breaks stuff down, provides more surface area for chemical weathering to occur. |
| What are the types of mechanical weathering? Name and describe them. | Frost wedging(h20 in pores freezes,expands), crys growth(salth20 crystallizes), therm expans(mineral’s crys structure grows with heat, knocks off things around it), mech exfol(eros frees rox, expand up & scrape off layers against immobile rock), roots. |
| Name and describe the ways in which chemical weathering occurs. | Dissolution (ion or ions are carried away by water), oxidation (ions combine with oxygen ions), hydrolysis (H+ or OH- replace ions). |
| What factors influence chemical weathering? | Climate (wet makes for more), living organisms (burrowing, etc.), time (more makes for more), mineral composition (stability and strength of chemical bonds). |
| What are some products of chemical weathering? | Clay minerals from hydrolysis of feldspars, rust from oxidation, metal ores, caves from dissolution, rounded boulders from spheroidal weathering (edges wear off; have more surface area). |
| Define regolith. | A fragmented material covering most of earth’s surface, created by erosion of sediment and bedrock. |
| Define “soil.” | The upper few meters of regolith that have minerals and organic material. |
| What factors influence soil formation? | Parent material, climate, topography, vegetation, and time. |
| Describe the common soil horizons. | Upper: O (organic matter, dead and live creatures), A (inorganic mineral material and humus), E (light-colored, little or no organic matter, eluviated); Lower: B (illuviated, materials from upper part), C (partially weathered parent rock), bedrock. |
| What is eluviation? | Water percolates down soil column, transports organic material and soluble inorganic matter. |
| What is illuviation? | Materials transported from upper soil horizons are deposited. |
| Define “sediment.” | The unconsolidated material that accumulates continuously at the Earth’s surface. |
| How are sedimentary rocks classified? | According to the source of their constituent materials as either detrital or chemical. |
| How do chemical sediments form? | From previously dissolved minerals that have precipitated from solution in water or extracted from water by living organisms and converted to shells or skeletons. |
| How do detrital sediments form? | From solid fragments of preexisting igneous, sedimentary, or metamorphic rocks. |
| How do we distinguish between types of detrital sediments? | Grain size and shape (angular or round). |
| What is lithification? | When sediments are turned into solid sedimentary rock. |
| Describe mudstones. | Most common detrital sedimentary rock, fine particles, turn into shale when put under pressure. |
| Describe sandstones. | Detrital sedimentary rocks: quartz arenites (mostly quartz, well-sorted and round), arkoses (pinkish, poorly sorted and angular), graywackes (dark, grey-to-green, mixture of quartz, feldspar, volcanic, mica, clay – poorly sorted). |
| Describe conglomerates and breccias. | Coarse detrital sedimentary rocks, have larger and smaller grains cemented together. Conglomorates are rounded and breccias are angular. |
| Describe inorganic limestone. | Chemical sedimentary rock, formed from evaporated calcite. |
| Describe dolostone. | Chemical sedimentary rock, composed of dolomite. |
| Describe evaporates. | Chemical sedimentary rock, deposited when salty water evaporates. |
| Describe inorganic chert. | Chemical sedimentary rock, have microscopic crystals of silica. Looks like nodes. |
| Describe biogenic limestone. | Made of calcite derived from the accumulation of calcium carbonate shells and skeletons. |
| Describe biogenic chert. | Layered rather than nodes. Made of organic silica things. |
| Describe coal. | Biogenic sedimentary rock, made of plant remains. |
| What are the four principles underlying relative dating? | 1) Original horizontality. 2) Superposition. 3) Cross-cutting relationships. 4) Principle of inclusion. |
| What is relative dating? | Comparing the physical characteristics and positions of two or more rocks to determine which is older and which is younger. |
| What is numerical dating? | Establishing the actual age of a geologic feature. |
| What kinds of rocks can become metamorphs? | Any type: sedimentary and igneous rocks. |
| Name the kind of pressure in the earth that is equal on all sides. | Lithostatic or confining pressure. |
| Name the kind of pressure in the earth that comes from two sides only. | Directed pressure. |
| What is foliation? | The arrangement of a set of minerals in parallel, sheet-like layers that lie perpendicular to the flattened plane of a rock. Occurs with directed pressure in metamorphic rocks. |
| Describe gneiss. | High grade metamorph, foliated, light and dark stripes. |
| Describe schist. | Strongly foliated, high grade metamorph, has large, visible flakes of mica. |
| Describe phyllite. | Foliated, glittery due to mica (not large). Medium grade metamorph. |
| Describe slate. | Foliated, low grade metamorph. Has slaty cleavage. |
| Describe marble. | High grade metamorph, non-foliated. Parent rock dolostone or limestone. |
| Describe quartzite. | Medium grade metamorph, non-foliated. Parent rock quartz sandstone. |
| Describe hornfels. | Low grade metamorph, non-foliated. Parent rock are shale, slate, or basalt, all water was taken away. Results in hard, dense, dark rock. |
| Why does marble fizz in acid? | It has calcite, which is acid soluble. |
| Why is it good to know whether or not the rock before you will fizz in acid? | Because that’s how you can tell between quartzite and marble. |
| What is hydrothermal alternation? | When water and magmatic gases mix and bring new ions to the material. |
| What are some sources of heat for metamorphic processes? | Decay of radioactive isotopes, intruding magma, friction between plates and rocks. |
| What are metamorphic rocks used for? | Building materials, sandpaper, beautification, bases of dams and jetties, blackboards, roads, energy. |
| What are the types of glaciers? | Alpine glaciers (cirque glaciers, valley glaciers, icecaps) and continental ice sheets. |
| What percentage of the earth is covered by glaciers? | 10%. |
| Define “glacier”. | A moving body of ice that forms from the accumulation and compaction of snow. |
| What is firn? | Dense, well-packed snow, formed from compressed snow underlying a light snowpack, when the contact points between crystals melts and refreezes. Becomes glacial ice. |
| Describe basal sliding. | When bottom of glacier melts due to pressure and lubricates so it moves. |
| What is a tarn? | A lake left by a glacier with mountains all around. |
| What is an arête? | A ridge formed between adjacent cirque glaciers. |
| What is a hanging valley? | A tributary valley with the floor at a higher relief than the main channel into which it flows. |
| What is a fjord? | A U shaped valley with a lake. |
| What is till? | Sediment directly laid down by ice. |
| What is a moraine? | A ridge formed of accumulated till, typically at the edge of a glacier. |
| What is an esker? | A ridge of sediment that forms under a glacier’s zone of ablation. |
| What is a roche moutonee? | An asymmetrical form, abraded on one side by an advancing glacier, and deeply quarried on the other side. Aligned along glacial flow. |
| Describe the Missoula Floods. | Lake Missoula (now Montana) was formed by a large river that was dammed by a huge piece of ice coming down from Canada. Water pressure built up, broke dam, floods everywhere. Happened 40x or so. |
| Where can earthquakes happen? | At any type of plate zones. |
| What does “seismic” mean? | Shaking. |
| What is an earthquake? | A trembling of the ground caused by a sudden release of energy in rocks below the surface. |
| Describe the types of seismic waves? | Primary waves (P-waves): 4 mi/sec, snapping motion. Secondary waves (S-waves) 2 mi/sec, wriggling motion. Surface waves move side to side and up and down. |
| How do geologists locate the epicenter of an earthquake? | Stations around the area can tell how far away the epicenter is, but not in what direction. If they draw circles around that are that distance away, where they intersect with other stations’ circles is where the epicenter is. |
| What is liquefaction? | Increase in water pressure between soil grains causes it to flow/form a slurry. |
| Describe the different types of describing earthquake strength. | Mercalli intensity scale (subjective), seismograph (sense and record on paper), Richter scale (from seismogram), Moment-Magnitude scale (measuring seismic moment). |
| What are some problems with the Richter scale? | Cannot effectively measure more than 7.0, seismographs are becoming obsolete, only effective with local quakes. |
| What are some effects of earthquakes? | Ground displacement, landslides and liquefaction, seiches, tsunami, fires. |
| What is a seiche? | When water in an enclosed body of water sloshes. |
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