Earth Science – Comprehensive Review

A set of question-and-answer flashcards covering Earth’s layers, plate tectonics, earthquakes, volcanoes, minerals, rocks, stratigraphy, fossils, geologic time, atmospheric science, climate change, energy resources, and depositional environments.

Which layer of the Earth occupies less than 1% of Earth’s volume and contains continental and oceanic plates?

The crust.

How much thicker is continental crust compared with oceanic crust?

Roughly three times thicker.

Which Earth layer makes up about 85% of Earth’s total mass and is roughly 1,800 miles thick?

The mantle.

What drives the movement of tectonic plates in the upper mantle?

Convection currents caused by heating and cooling of mantle material.

What are the two parts of Earth’s core called?

The liquid outer core and the solid inner core.

What is the depth of the outer core beneath Earth’s surface?

Approximately 3,000 miles.

Name the point below ground where an earthquake originates.

The hypocenter (focus).

What term describes the point on Earth’s surface directly above an earthquake’s hypocenter?

The epicenter.

What type of plate boundary involves two plates colliding head-on, often producing a thrust fault?

A convergent boundary.

During ocean-continent convergence, what happens to the denser oceanic plate?

It is subducted into the mantle where it melts, sometimes producing volcanoes on the continental plate.

Which plate boundary pulls apart to form a rift zone and new ocean floor?

A divergent boundary.

At what type of boundary do two tectonic plates slide past each other and build up shear stress?

A transform boundary.

What kind of stress produces a normal fault and results in crustal extension?

Tensional stress.

Compressional stress produces which type of fault?

A reverse (thrust) fault.

What kind of fault is associated with shear stress and horizontal movement?

A strike-slip fault.

How is earthquake magnitude defined?

It is a calculated, fixed value that measures the energy released at the source.

What does earthquake intensity measure?

The strength of shaking, based on human perception and observed damage, which decreases with distance.

What four diagnostic tests are part of mineral identification?

Hardness, luster, streak, and cleavage/fracture.

How is cleavage different from fracture in minerals?

Cleavage breaks predictably along planes; fracture breaks irregularly.

What scale is used to measure mineral hardness?

The Mohs hardness scale.

From what process do igneous rocks form?

Cooling and solidification of magma or lava.

What distinguishes intrusive from extrusive igneous rocks?

Intrusive rocks cool slowly underground (large crystals); extrusive rocks cool quickly at the surface (small or no crystals).

Which rock type forms by lithification of sediment through compaction and/or cementation?

Sedimentary rock.

What are the three main categories of sedimentary rocks?

Clastic, crystalline (chemical), and bioclastic (organic).

Metamorphic rocks are produced by exposure to what two main agents?

Intense heat and/or pressure.

Which principle of stratigraphy states that the oldest rock layers lie at the bottom of an undisturbed sequence?

The principle of superposition.

What does the principle of cross-cutting relationships indicate about relative ages?

A rock or fault that cuts across layers is younger than the layers it cuts.

A gap in the geologic record created by erosion or non-deposition.

Unconformity

Which fossils are most useful for correlating rock layers of the same age in different locations?

Index fossils.

List the four geologic eons in order from oldest to youngest.

Hadean, Archean, Proterozoic, Phanerozoic.

During which era did dinosaurs dominate Earth?

The Mesozoic Era.

What major biological event marks the start of the Paleozoic Era?

The Cambrian Explosion.

Which period within the Cenozoic Era saw the evolution of modern humans?

The Quaternary Period.

What volcanic landform is broad, gently sloping, and built almost entirely from basaltic lava flows?

A shield volcano.

Which type of volcano forms steep slopes, alternating layers of lava and tephra, and often produces pyroclastic flows?

A composite (stratovolcano).

Name the two basaltic lava surface textures common to shield volcanoes.

Pāhoehoe (smooth/ropy) and ʻAʻā (rough/blocky).

A location where a mantle plume rises, creating volcanism away from plate boundaries.

Volcanic hotspot

Explain the difference between felsic and mafic lava in terms of viscosity and gas content.

Felsic lava is silica-rich, cooler, more viscous, and gas-rich (explosive); mafic lava is hotter, less viscous, and gas-poor (effusive).

Which atmosphere layer contains the ozone layer and is where commercial airplanes typically cruise?

The stratosphere.

Where do auroras occur within Earth’s atmosphere?

The thermosphere.

How does a cyclone (low-pressure system) rotate in the Northern Hemisphere?

Counterclockwise, bringing clouds and storms.

Which cloud type is tall and capable of producing thunderstorms?

Cumulonimbus clouds.

What is the greenhouse effect?

The trapping of outgoing infrared heat by greenhouse gases such as CO₂, CH₄, H₂O vapor, and N₂O.

Name two positive feedback loops that can amplify global warming.

Melting permafrost releasing methane; loss of Arctic ice decreasing albedo.

Define renewable energy and give two examples.

Energy sources that are naturally replenished, e.g., solar and wind energy.

Why are non-renewable resources considered unsustainable in the long term?

They are finite and their use releases greenhouse gases contributing to global warming.

What fluvial depositional feature forms fan-shaped sediment deposits at river mouths?

A delta.

Which glacial depositional landform is a ridge of unsorted sediment deposited at a glacier’s edge?

A moraine.

What aeolian landform consists of wind-blown silt deposits that create fertile soils?

Loess.

Define lateral continuity in stratigraphy.

Sedimentary layers initially extend laterally in all directions until they thin out or encounter a barrier.

What is an anticyclone and what kind of weather does it usually bring?

A high-pressure system rotating clockwise in the Northern Hemisphere; it brings clear, fair weather.

Which air mass is warm and moist: maritime tropical (mT) or continental polar (cP)?

Maritime tropical (mT).

Name three major greenhouse gases.

Carbon dioxide (CO₂), methane (CH₄), and water vapor (H₂O).

What type of volcanic eruption produces tephra and volcanic bombs from explosive gas release?

An explosive eruption, typical of felsic volcanoes.

Which depositional environment is characterized by dunes and is common in deserts?

Aeolian environment.

What principle states that sedimentary layers are originally deposited horizontally?

The principle of original horizontality.

In plate tectonics, what large ancient landmass broke apart to create today’s continents?

Pangaea.

What feature on the ocean floor marks a divergent boundary where new crust forms?

A mid-ocean ridge (rift zone).

What hazard is often produced by stratovolcanoes when viscous lava domes collapse or explode?

Pyroclastic flows.

Which large-scale volcanic feature involves massive, rapid outpourings of basaltic lava that create plateaus?

Large Igneous Provinces (LIPs) or flood basalts.

What type of rock ends with the suffix "-gneiss" or "-schist"?

Metamorphic rock.

Describe the process that forms fossils beginning with burial.

Burial → sedimentation → mineralization, preserving body or trace evidence of life.

What are kimberlite pipes and why are they important geologically?

Deep magma conduits that carry ultramafic magma from great depths; they often contain diamonds and high-pressure minerals.

Which atmospheric layer is the coldest and where meteors burn up?

The mesosphere.

What is the main difference between weather and climate?

Weather is short-term atmospheric conditions; climate is long-term average patterns.

Which cloud type appears as thin, wispy strands at high altitude and indicates fair weather?

Cirrus clouds.

What is the term for matching rock layers of similar age in different locations?

Correlation.

What depositional landform forms where a river exits a mountainous area and abruptly loses energy, producing a cone-shaped deposit?

An alluvial fan.

Name two common landforms created by wind deposition along coastlines.

Beaches and barrier islands.

Which principle allows geologists to determine that horizontal lava flows above tilted sedimentary layers are younger than the tilted layers?

Cross-cutting relationships (the lava flow cuts across older tilted strata).

What property of minerals is tested by rubbing them on a porcelain plate to observe powder color?

Streak.

What large-scale oceanic process helps redistribute heat globally and influences climate?

Ocean currents driven by temperature and salinity differences.

Which renewable energy source harnesses heat from Earth’s interior?

Geothermal energy.

Define a deltaic depositional environment and list one classic delta shape.

It forms where a river meets standing water; one shape is the arcuate (fan-shaped) delta.

A sandbar that connects an island to the mainland.

Tombolo

How does albedo affect Earth’s climate?

High-albedo surfaces reflect sunlight and cool Earth; low-albedo surfaces absorb heat and warm Earth.

The surface along which two blocks of crust slip during an earthquake.

Fault plane