Geology Exam 2

2. What are the characteristics of aquifer, aquiclude, and aquitard rocks? (Define each of those terms and indicate what type of rock can serve in that role)

Acquifier: Stores water and allows extraction. Get ground water from. Ex: sandstone, coarse clastic sedimentary rocks, fractured/weathered granite and basalt Aquitard: Holds and slows water flow. Low permeability, regardless of porosity. Some porosity. Ex: shales Aquiclude: Impermeable, no extraction. ex: clays and shales

2. What portions of the earth does Plate Tectonics affect?

Lithosphere and Asthenosphere; crust and mantle

3. Define Lithosphere and Asthenosphere: layers of the Earth according to the "physical behavior" of materials. Characteristics. Know their thickness and relationships with the "chemical compositions" layers of the earth: core, mantle, crust.

Lithosphere: outer solid layer; crust and upper mantle; brittle and elastic; thinnest under oceans = Ca, Na, K, Mg, Fe (crust) silicates Fe, Mg (mantle) Asthenosphere: Mantle, flows plastically. Silicates of Fe, Mg = mantle

7. Observing the type of construction in Costa Rica, indicate what type of buildings are better suited to withstand a large earthquake?

Metal frame anchored in the bedrock. Use materials that bend rather than break. Examples: reinforced concrete, wood structures are better than concrete.

4. What factors need to be considered in order to assess ground water availability? Explain how any two of them influence the groundwater system.

Two factors would be recharge area and behavior with a river. An unconfined aquifer has a larger recharge area making it easier to collect rainfall. The aquifers behavior with a river is good for the aquifer if it recieves water from the river but is bad if the river takes water from it. Other factors are climate and demand.

10. How do floodplain developments affect stream behavior and why? Give examples

Water loses its velocity and causes coarser grained suspended sediments to be deposited along the river bank -> builds natural lives which prevent future flooding.

5. How do you measure water quality?

Water quality is measured in ppm, ppb, or TDS (total dissolved solids) which is the total dissolved chemicals in the water. Chemicals dissolved are As, cyanide, ppbs, sulfur, Fe, calcium, magnesium, and Hard Waters (more than 80 ppms Ca or Mg), PH, or Microinvertabrates.

10. What is the status of earthquake prediction? What are seismic gaps? Earthquake precursors?

We cannot 100% predict earthquakes. *Seismic gaps* is a segment of an active fault that has not had an earthquake in a while. *Earthquake Precursors* give effective warnings of earthquakes; example: groundwater levels or animal behaviors.

11. What measures can be taken to minimize loss before, during and after an earthquake?

*Before*: Build structures with materials that bend rather than break. Especially wood structures rather than brick and metal frames anchored in bedrock. *During*: Drop, Cover, and Roll. Stay inside rooms without windows. *After*: Eliminate fire hazards by cleaning up flammable liquids and putting out small fires.

8. Tsunami hazard. What is a tsunami? Where would its impact be more severe?

*Tsunami* is large waves originated by underwater earthquakes or landslides. It's impact is most severe along coasts because waves are more severe closer to the source.

6. Hazards related to earthquakes. Which preventative mitigating measures can be taken to minimize impact? The problem of old buildings. Behavior of different types of material (sediment and hard rocks) during an earthquake. Man-made earthquakes.

1) Planning and thoughtful design- ex. power lines and pipe lines should be built with extra slack where they cross a fault zone. 2) Building codes for "earthquake resistant" buildings 3) Build on solid bedrock rather than deep soil. 4) Avoid building near fault zones. 5) Man made earthquakes are from injecting liquid into the earth- typically done for fracking to extract oil and can cause earthquakes from tension buildup.

9. How can conservation be applied to save water? Explain in detail two options.

1. Moderating irrigation: the raising of crops that require a great deal of water could be shifted to areas where natural rainfall is adequate to support them. 2. Drip irrigation: instead of running irrigation water in open ditches from which evaporation loss is high, the water can be distributed via pipes with tiny holes from which water sleeps slowly into the ground at a rate more closely approaching that at which plants use it.

Non-point source

A source of pollution that issues from widely distributed or pervasive environmental elements. Examples: fertilizer runoff from farmland, acid drainage from abandoned ship mine

1. Where would you expect earthquakes to occur and why?

Along faults; because a fault is displacement of one side relative to the other along faults. Also creeps occur here which is gradual fault movement.

Elastic deformation

Amount of deformation is proportional to stress applied and material returns to original shape

5. What are the physical characteristics of the asthenosphere and the lithosphere?

Asthenosphere: Partially molten layer of mantle below the lithosphere; behaves plastically. Lithosphere: Rigid and solid formed by the crust and uppermost mantle; behave brittle.

5. Compare and Contrast Magnitude and Intensity. What does each of them measure and how do they vary in relation to the place where they are measured?

Both magnitude and intensity measure different characteristics of earthquakes. - Magnitude measures the ENERGY released at the SOURCE of the earthquake (epicenter). It is determined from measurements on seismographs. - Intensity measures the strength of shaking produced by the earthquake at a certain location. It is determined from effects on people, human structures, and the natural environment.

4. What is a stream's discharge and how do you measure it?

Discharge: volume of water flowing past a given point for a specified length of time. Discharge = area * velocity

12. How does the behavior of a river change when a dam is build? what are the advantages and disadvantages?

Changes base level sediment deposition in the reservoir and shapes the stream channel. Advantages: Controls water flow to reduce flooding Disadvantages: Deprives areas downstream from sediment erosion, causes displacement, treasures, and artifacts lost.

Geologic stresses

Compression, tension, and shear

8. What is a cone of depression? What lies point out to excessive groundwater withdrawal? Mention its consequences.

Cone of depression- a circular lowering of the water table immediately around the well, in an unconfined aquifer. Clues include 1. Cone of depression - consequences include regional lowering of water table. 2. Compaction and Surface Subsidence- due to the empty poral spaces not being able to support the rock above. Consequences could lead to flooding and lowering of land. This could risk losing an aquifer. 3. Salt water intrusion- consequence is that once section of aquifer becomes tainted by salt, it can't be made fresh again. 4. Loss of recharge- consequences could lead to loss of groundwater and aquifers. Solution - artificial recharge basin.

1. Sources of the heat that drives earth's internal system

Decay of radioactive elements in the Earth and accretion/differentiation

15. How can the rate of plate movement be determined? Describe at least one way to do so, indicating the data needed and how it would be obtained. Remember that you will have to calculate a velocity.

Determined by polar wander curves from continental rocks, used to show continents have shifted. Seafloor spreading: rate. dates rocks at different distances from spreading and dividing distances moved by rocks age: distance/time.

10. The three types of plates boundaries are convergent, divergent, and transform. What happens with the plates at each of them?

Divergent: Plates move apart Convergent: Plates move toward each other Transform: Moves in opposite directions

11. Characterize the types of stress and magmatism related to each type of boundary.

Divergent: Tensions; normal or direct Convergent: Compression; reverse Transform: Shear; strike slip fault or transform fault

3. How does the depth of earthquake focus vary according to tectonic setting?

Focus is the point of first rupture at depth; mid-ocean ridges occur at 0-70 km depth and are shallow; subduction zones occur at 70-350 km and are intermediate; intraplate settings occur at 350-700 km and are deep and severe

6. What do you understand by hard waters? What does pH measure? When is water considered alkaline and when acidic?

Hard water- contains substantial amounts of dissolved calcium and magnesium (more than 80ppms). pH- measures how acidic or basic/alkaline water is by the relative amount of free hydrogen ions H+ (indicates acidity) and hydroxide ions OH- (indicates alkaline). 0-6.99 = acidic 7 = neutral 7.01- 14 = alkaline/basic

16. Hot spots: What is a hot spot? Why is there volcanism at hot spots? Where does the magma in hot spots come from? What type of magma is common at oceanic hot spots?

Hot spot are isolated areas of volcanic activity usually not associated with plate boundaries. Volcanism is at hotspots bc of warm mantle material that rise up through colder, denser mantle. Reduction in pressure as plume increases leads to partial melting and magma can work its way through overlying plate -> the melts are balsamic.

2. Why do earthquakes occur in Costa Rica?

It's built on a fault line

5. Describe the different ways that large boulders, sand and clay are transported in a stream.

Large boulders are rolled, dragged or pushed along a stream bed as a traction load (bed load) Sand: saltation (short hops long the stream bed) Clay: Suspension

9. How does a river create a floodplain?

Made by a Mander eroding side banks and then floods, leaves behind layers of alluvium - gradually builds up to create the floor and floodplain

13. Describe the igneous activity (rock composition) and geologic process (volcanism?, metamorphism?, igneous intrusion?) in each of the convergent plate boundaries?

Ocean-ocean: older earth goes down. String of volcanic islands Oceanic-continent: seafloor goes under, volcanoes form on continent and trench is partially filled by sediment. Continent continent: No subduction. earthquakes and mountains.

12. What differences exists in the type of lithosphere meeting at the three kinds of convergent plate boundaries? What happens with them?

Oceanic continental seafloor is consumed and volcanoes form an overriding continent. Oceanic ocean: creates string of volcanoes islands, molten material rises to surface. Continental continental : sublate meets overriding plate which creates great thickness of the continental lithosphere.

9. What logical conclusion about the continents (or rather lithosphere) can be drawn from the reality of seafloor spreading and the ages of the ocean floor?

Plate tectonics are moving. All of the continents were connected.

11. Measures to reduce flood hazard. Advantages and disadvantages.

Retension ponds: slow down water and allow infiltration and evaporation. Artificial levees: raise sides of banks but provide a false sense of security. Channelization: Modifications of stream channels. Dams

Brittle material

Ruptures occur before any plastic deformation

3. What is an artesian system? Compare its recharge area to that of an unconfined aquifer. Define potentiometric surface.

Same thing as a Confined aquifier. Water rises above aquifier level from extra hydrostatic pressure. Does not required pumping. Free flow water. Unconfined- recharged near surface, threatened by development. Artesian (confined)- can't be recharged by infiltration from above When pressure in a confined aquifier pushes the water out, it would be how high the water shoots up.

7. How does clastic sediment change along the longitudinal profile of a stream?

Sediment becomes finer through breakup and sorting along the longitudinal profile

Point source

Sources from which pollutants are released at one readily identified spot; easier to identify as potential pollution problems. Examples: sewer outlet, steel mill, septic tank

7. How did paleomagnetism and magnetic reversals help to support the idea of seafloor spreading? How does seafloor spreading occur?

Support: Basaltic rock becomes magnetized, showing the direction of Earth's magnetic field, As the plates part, young rock split and magma makes younger rocks. If the polarity of the Earth's magnetic field reverses during sea floor spreading the rocks formed after the reversals are polarized oppositely from those that formed before. How it occurs: oceanic plates move apart creating a rift and mantle flow upward and cools, forming a new sea floor

6. How does gradient change along the longitudinal profile of a stream?

The gradient decreased from source to mouth.

8. What are the characteristics of the seafloor ages with reference to mid oceanic ridges?

The oldest rocks are the furthest from the mid oceanic ridge and the youngest are the closest to the ridge

6. Earth's Magnetic field. What is Paleomagnetism?

The property of ferromagnesian minerals align themselves parallel to the lines of force of the magnetic field of earth when they form. This orientation preserves the location of the magnetic north at the time of crystallization. * The "fossil magnetism" preserved in the rocks formed in the past *

4. Types of waves: body and surface waves. What are their characteristics? (Media they travel through, relative velocities, type of movement with reference to the direction of travel, are they compressive or shear?) ** Make sure you do not mix up s waves with surface waves! **

There are 2 types of body waves: Primary (P-wave) and Secondary (S-wave). * TRAVEL INSIDE THE EARTH * - Primary (COMPRESSIVE) Travel: Through solids and liquids. Velocity: Fast Movement: Shake the ground in the direction they are propagating - Secondary (SHEAR) Travel: Through solids (not liquid or gasses) Velocity: Slower than p-wave Movement: Move perpendicular to the direction of travel There is 1 type of surface waves (SHEAR) * MOST DESTRUCTIVE * Travel: Move along the surface Velocity: Slowest Movement: Arrive last of the waves

4. Evidence for plate movement: examples gathered by Alfred Wegener who proposed Continental Drift and Harry Hess, who proposed Seafloor Spreading.

Wegener: Fossil distribution - same fossils in India, Africa, Antartica (bondwana)(; Paleozoic glaciation glaciers move out. mid point in Africa. Harry Hess: used sonar to discover underwater mountains at varying states of erosion. Believed this was due to seafloor spreading.

Plastic deformation

When small amounts of force yield large amounts of deformation; object does not return to original shape

Plastic material

ability of certain solids to flow or to change shape permanently when subjected to stresses of intermediate magnitude between those producing temporary deformation, or elastic behaviour, and those causing failure of the material, or rupture

Affect of heat and pressure on geologic materials

rocks tend to behave more plastically at higher temperatures than at lower ones; Confining pressure is that uniform pressure which surrounds a rock at depth. Higher confining pressure also tends to promote more-plastic, less-brittle behavior in rocks. Confining pressure increases with depth in the earth, as the weight of overlying rock increases; temperature likewise generally increases with depth