Geology and Earth Systems Review

A comprehensive set of practice flashcards covering geology topics including seismology, planetary structure, rock deformation, dating techniques, energy resources, hydrogeology, and glaciology based on lecture notes.

How do earthquakes occur along faults?

Earthquakes occur when stress builds up along a fault until rocks suddenly break and slip, releasing stored energy as seismic waves.

In what kind of geologic media are seismic waves amplified the most?

Seismic waves are amplified the most in soft, unconsolidated sediments such as sand, mud, or landfill material.

How do P-waves, S-waves, and surface waves move?

P-waves compress and expand material in the direction of travel, S-waves move material perpendicular to travel, and surface waves move in rolling or side-to-side motions along Earth’s surface.

What are some possible warning signs of an impending earthquake?

Possible warning signs include small foreshocks, unusual animal behavior, ground deformation, and changes in groundwater levels.

How is the epicenter of an earthquake determined using seismic stations?

The epicenter is found by comparing the arrival times of P-waves and S-waves at at least $3$ seismic stations and triangulating the location.

In what geologic setting do the deepest earthquakes occur?

The deepest earthquakes occur in subduction zones where one tectonic plate sinks beneath another.

What are the three major compositional layers of the Earth and their characteristics?

The crust is thin and rocky, the mantle is dense and slowly flowing, and the core is metallic and mostly iron and nickel.

What are the characteristics of the physical layers of the Earth?

The lithosphere is rigid, the asthenosphere is soft and plastic, the mesosphere is stronger mantle rock, the outer core is liquid, and the inner core is solid.

What evidence proves the outer core is liquid?

S-waves cannot travel through liquids and disappear when reaching the outer core.

What information do gravity surveys provide about the Earth’s subsurface?

Gravity surveys provide information about differences in rock density beneath Earth’s surface.

What is the difference between positive and negative magnetic anomalies?

Positive magnetic anomalies are areas with stronger-than-average magnetic fields, while negative anomalies are areas with weaker-than-average magnetic fields.

What geologic structures are produced by tensional, compressional, and shearing stresses?

Tensional stress forms normal faults, compressional stress forms reverse faults and folds, and shearing stress forms strike-slip faults.

What are the main stages and types of coal?

Coal forms from buried plant material altered by heat and pressure. The main types are peat, lignite, bituminous, and anthracite.

How can anticlines and synclines be distinguished in map view?

In map view, anticlines usually have older rocks in the center, while synclines have younger rocks in the center.

What geologic evidence indicates the presence of a fault?

Evidence includes offset rock layers, fault scarps, slickensides, crushed rock zones, and displaced streams or roads.

What are the definitions of 'strike' and 'dip'?

Strike is the compass direction of a rock layer or fault, while dip is the angle at which it slopes downward.

Why do continental lithosphere and magmatic island arcs resist subduction?

They are too buoyant and less dense than oceanic lithosphere.

Why are sedimentary rocks typically deposited in horizontal layers?

Sediments settle under gravity in flat layers, creating horizontal deposits.

What are the principles of relative dating?

The principles include superposition, original horizontality, cross-cutting relationships, inclusions, faunal succession, and lateral continuity.

What are the three main types of unconformities?

Angular unconformities separate tilted rocks from horizontal layers, nonconformities separate sedimentary rocks from igneous or metamorphic rocks, and disconformities separate parallel sedimentary layers with missing time between them.

How do scientists use radioactive decay to date rocks?

Scientists measure the ratio of radioactive parent isotopes to daughter isotopes to calculate a rock’s age.

What are the characteristics of an index fossil?

An index fossil is widespread, easily recognized, and existed for a short geologic time span.

What is the significance of the Precambrian-Cambrian time boundary?

It marks the Cambrian Explosion, when many complex life forms rapidly appeared in the fossil record.

What percentage of U.S. energy consumption is provided by fossil fuels?

Fossil fuels (coal, oil, and natural gas) provide about $80\%$ of U.S. energy consumption.

What are the steps in forming a conventional petroleum or natural gas deposit?

Organic matter accumulates, is buried, transforms through heat and pressure, migrates through porous rock, and is trapped beneath impermeable rock.

What are the four main types of geologic traps for petroleum and natural gas?

The main traps are anticlines, fault traps, salt domes, and stratigraphic traps.

How does hydraulic fracturing ('fracking') work?

High-pressure fluid is injected into rock to create fractures that release oil and gas.

Which element is primarily used for nuclear energy production?

Uranium is most commonly used.

What defines a hydrothermal ore deposit?

A hydrothermal ore deposit forms when hot, mineral-rich fluids move through rocks and deposit valuable minerals.

What are the main ingredients used to make concrete?

Concrete is made of cement, water, sand, and gravel or crushed stone.

What factors influence the speed and direction of groundwater flow?

Groundwater flow depends on permeability, porosity, hydraulic gradient, and rock type.

How does karst topography form?

It forms when acidic groundwater dissolves limestone, creating caves, sinkholes, and underground streams.

What is the primary source of most shallow groundwater in the Earth's crust?

Most shallow groundwater comes from precipitation that infiltrates into the ground.

What does Darcy’s Law describe?

Darcy’s Law describes the relationship between groundwater flow rate, permeability, and hydraulic gradient.

What is the effect of pumping groundwater from a well?

Pumping lowers the water table around the well, creating a cone of depression.

How do glaciers form?

Snow accumulates, compresses into firn, and eventually recrystallizes into dense glacial ice.

How are glacial striations and glacial polish formed?

They are produced when rocks embedded in moving ice scrape and smooth bedrock surfaces.

What are the major landforms produced by glaciers?

Major landforms include moraines, drumlins, eskers, cirques, arêtes, fjords, and U-shaped valleys.

What are Milankovitch cycles?

Milankovitch cycles are changes in Earth’s orbit, tilt, and wobble that affect climate and contribute to ice ages.

What is glacial rebound?

Glacial rebound occurs when the land moves upward after the weight of melting continental-scale glaciers is removed.

How much more energy is released in a magnitude $5$ earthquake compared to a magnitude $4$ earthquake?

A magnitude $5$ earthquake has $10$ times greater shaking amplitude and about $32$ times more energy release than a magnitude $4$ earthquake.

What are the primary causes of tsunamis?

Tsunamis are mainly caused by undersea earthquakes, volcanic eruptions, or landslides.

What is the difference between body waves and surface waves?

Body waves travel through Earth’s interior, while surface waves travel along the surface and typically cause the most damage.

Define elastic, brittle, and ductile rheology in rocks.

Elastic materials return to their original shape, brittle materials break, and ductile materials bend without breaking.

How do you distinguish a dome from a basin in map view?

A dome has older rocks in the center with layers dipping outward, while a basin has younger rocks in the center with layers dipping inward.

What is the difference between a joint and a fault?

A joint is a crack with no movement, while a fault is a fracture along which movement has occurred.

What is the currently accepted age of the Earth?

Earth is about $4.54$ billion years old.

What is an aquifer?

An aquifer is a rock or sediment layer that stores and transmits groundwater.

What is hydraulic head?

Hydraulic head is the total energy that drives groundwater flow, combining elevation and pressure.

How do groundwater characteristics change with increasing depth?

With increasing depth, groundwater generally becomes warmer, more mineral-rich, and moves more slowly.