Geology Study Guide

A geologist studies sand ripples forming in a modern river to help interpret similar ripple patterns preserved in 300-million-year-old rock. This approach relies on which principle?

Uniformitarianism

According to the reading, which of the following best describes what geology actually studies?

Earth's interior, surface, materials, and the processes that shape them — using tools from many other sciences

According to the reading, which of the following is NOT commonly given as a reason to study Earth?

Predicting the exact date of the next earthquake down to the day

A geologist proposes an untested explanation for why a rock layer formed the way it did. In scientific terms, this initial explanation is called a:

Hypothesis

In 1971, a major earthquake struck the San Fernando Valley in California, revealing that some structures had been built directly on top of active fault lines. Geologists cannot predict exactly when or where the next earthquake will strike — but state lawmakers still wanted a long-term, science-based solution rather than just rebuilding and hoping for the best. What course of action did California ultimately take?

Require the State Geologist to map active faults and mandate a geologic investigation before construction is approved in those zones

Which idea is most often cited as the aspect of geology that sets it apart from sciences like physics and chemistry?

The vast amount of time needed to understand many Earth processes — thousands to billions of years

Earth's surface is divided into large pieces that move and interact with one another, a concept known as ______.

Plate tectonics

California's Salton Sea region has been nicknamed “Lithium Valley” because geothermal brines deep underground there are estimated to hold millions of tons of lithium — a critical ingredient in EV batteries — making it one of the largest known lithium resources in the country. Before any company can build a large-scale extraction facility there, what must happen first?

Geologists must study the subsurface to locate the brine reservoir, estimate how much lithium it holds, and assess whether extraction is feasible

What ancient organism produced most of Earth's early atmospheric oxygen through photosynthesis?

Stromatolites

What evidence found in the bedrock of New York City's Central Park points to a past ice age?

Small parallel grooves cut into the bedrock by rocks trapped under moving glacial ice

Who calculated the age of Earth using thermodynamics and concluded — incorrectly — that the planet was only about 20 million years old?

Lord Kelvin

Select ALL of the following that are true about the oxygenation of Earth's atmosphere and oceans:

• Dissolved iron in the ocean reacted with new oxygen to form solid mineral deposits

• Oxygen levels rose gradually over hundreds of millions of years

• Photosynthetic organisms released oxygen as a byproduct

Select ALL of the following that are presented as possible sources of Earth's water:

• Volcanic outgassing from Earth's interior

• Rainfall as Earth's early steamy atmosphere gradually cooled

• Water delivered by comets and/or meteorites

According to the reading, planets form out of a rotating disk of leftover gas and dust surrounding a young star. What is this disk called?

A protoplanetary disk

What piece of evidence, discussed in both the reading and the documentary, supports the Big Bang theory for the origin of the universe?

Cosmic microwave background (CMB) radiation

What is identified as the likely cause of the Permian mass extinction (~250 million years ago)?

A large meteor impact in Mexico

The K-Pg (dinosaur) extinction is supported by a thin, worldwide clay layer containing unusually high concentrations of which rare element?

Iridium

Select ALL of the following that are described as part of Earth's projected long-term future:

• Earth's long-term habitability depends on plate tectonics continuing

• Another ice age is expected in the relatively near future (geologically speaking)

• Continents will eventually collide again to form a new supercontinent

Select ALL of the following that provided evidence supporting the theory of plate tectonics:

• Matching fossils found on separated continents

• The jigsaw-puzzle-like fit of continental coastlines

• Mapping of the ocean floor after World War II

Why is granite (continental crust) able to "float" higher than denser oceanic (basaltic) crust?

Granite is less dense than basalt

What layered rock deposit formed when oxygen reacted with iron dissolved in Earth's early oceans?

Banded iron formation

Which process listed below is one of the drivers of the movement of Earth's tectonic plates?

onvection currents within the mantle

Select ALL of the following that contributed to determining the true age of Earth, according to the documentary:

• Lord Kelvin's thermodynamics calculations

• James Hutton's observations of rock layers at Siccar Point

• Arthur Holmes's use of radiometric (radioactive) dating

According to the documentary, what type of rock structure is used as evidence that oceans already existed on Earth as far back as 3.5 billion years ago?

Pillow lava

What fossil evidence puzzled early geologists and helped inspire Alfred Wegener's theory of continental drift?

A freshwater trilobite (Paradoxides) found on both sides of the Atlantic Ocean

What is the origin of the rock at the summit of the Matterhorn in Switzerland?

It is a piece of the African continental plate resting on top of the European plate

According to the documentary's long-term projections, what will eventually happen to New York City as a new supercontinent (Pangaea Ultima) forms hundreds of millions of years in the future?

It will be crushed and thrust upward as new mountains form from a continental collision

According to the reading, terrestrial (rocky) planets like Earth are composed primarily of which materials?

Rock and metal

____ at the magnetic equator.

horizontal

____ at the magnetic poles

vertical

Earth's magnetic field is generated by:

Convection of liquid iron in the outer core

Which statements about isostasy are correct?

• Adding weight (such as a growing ice sheet) causes the crust to sink deeper into the mantle

• Continental crust floats higher on the mantle than oceanic crust

• The mantle behaves as a non-Newtonian fluid, deforming differently depending on how quickly stress is applied

Rocks richer in silica are described as _____ .

felsic

The mantle as a whole, which has even more iron and magnesium than mafic rock us described as ____ .

ultramafic

Rocks with less silica but more iron and magnesium are described as ____ .

mafic

Listed from outermost to innermost, which set correctly names Earth's three main "compositional" layers?

Crust, mantle, core

The boundary between the crust and the mantle, identified by a sharp change in seismic wave velocity, is known as:

The Mohorovičić discontinuity (the "Moho")

If a large mountain range erodes away over tens of millions of years, what happens to the crust beneath it?

It slowly rebounds upward as mantle material flows back underneath

A seismic "shadow zone" is best defined as:

A region on Earth's surface where certain seismic waves fail to arrive following an earthquake

Earth's internal heat comes from two main sources. Which pairing correctly identifies them and how their contribution has changed since Earth formed?

Radioactive decay (ongoing, but decreasing over time) and heat from formation — collisions, compression, and differentiation (a one-time input from early Earth)

Why does mantle rock remain mostly solid even at temperatures well above 1,000°C?

High pressure at depth raises the melting point of mantle rock above the actual temperature there

Why is almost everything we know about Earth's mantle and core based on indirect evidence?

Because the deepest borehole ever drilled is far shallower than the mantle, so direct observation isn't possible

A seismic station records a P-wave arrival but no S-wave arrival following a large, distant earthquake. What is the best interpretation?

The wave's path passed through a liquid layer at some point

Which statements about meteorites and Earth's interior are correct?

• Stony meteorites are thought to resemble fragmented mantle material

• These meteorites came from asteroids that differentiated into a mantle and core, similar to Earth

• Iron meteorites are thought to resemble fragmented core material

Today, __________ is in about the same geographic position as during late Paleozoic time

Antarctica

Which one of these statements supports the theory that Pangaea was once covered by glaciers?

glacier scrapes on rocks

New seafloor is created where two oceanic plates ______ from each other.

move apart (diverge)

Wegener was unable to explain the forces that could move continents. What mechanisms do geologist think help move the plates? Select all that are correct.

Answer,

• ridge push

• slab pull

• convection currents

At a transform boundary, two plates grind past each other...

without creating or destroying crust

Some early geologists believed continents and oceans have always stayed roughly where they are now. In their view, mountains formed when a thick pile of sediment called a ______ later got squeezed and folded.

geosyncline

The Earth's magnetic field is preserved in the basaltic oceanic rock because this rock contains the mineral ____________. 

magnetite

An oceanic plate subducting beneath a continental plate (as along South America's Andes or the U.S. Pacific Northwest) typically produces a...

continental volcanic arc

What is the predicted fate of the Atlantic Ocean in the distant future based on the Wilson Cycle?

It will eventually close as the oceanic lithosphere breaks away and begins to subduct.

Most of Earth's transform faults are found...

on the ocean floor, offsetting segments of mid-ocean ridges

Which scientist developed the continental drift hypothesis?

Alfred Wegener

Before radioactivity was understood, some geologists proposed that Earth's mountains formed because the planet was shrinking as it cooled from an originally molten state (contractionism). In the early 1900s, scientists discovered that radioactive elements inside Earth continuously generate new heat. What does this discovery imply about contractionism?

It undermines contractionism, because Earth is not simply cooling and shrinking over time the way the theory assumed

Which type of plate boundary tends to produce the largest and deepest earthquakes?

Convergent boundaries

What idea brought a renewed interest to the idea of continental drift?

Data that a submarine mountain occurred beneath the middle of the Atlantic Ocean

All of the following are types of plate boundaries, EXCEPT:

hot spots

Why are mid-ocean ridges higher in elevation than the surrounding ocean floor?

The warmer rock near the ridge is less dense, so it floats a bit higher on the mantle.

Hess's theory of seafloor spreading was later supported by the discovery of magnetic anomalies in the rock on the sea bed which indicate that ____ .

as new seafloor is generated, the paleomagnitism is recorded as the rocks cool.