Earth and Space Sciences: Geology, Plate Tectonics, and the Rock Cycle

Comprehensive practice flashcards covering Earth layers, plate tectonics, volcanoes, earthquakes, minerals, igneous, sedimentary, and metamorphic rocks, weathering, erosion, and the rock cycle.

What are the four primary concentric layers that make up the structure of the Earth?

The crust, mantle, outer core, and inner core.

What does the Earth's crust consist of and what is its physical state?

It consists of landforms, rocks, and soil, and is mostly solid rock.

What is the typical thickness range of the Earth's crust?

$5\,\text{km}$ to $70\,\text{km}$ (also shown up to $100\,\text{km}$ in general lithospheric diagrams).

What two distinct mechanical layers comprise the upper mantle?

The lithospheric mantle (more solid) and the asthenosphere (more liquid).

Which two structures combine to make up the Earth's lithosphere?

The crust and the solid uppermost part of the mantle (lithospheric mantle).

What state of matter is the Earth's lithosphere?

Solid.

What major structural units are formed by the rigid lithosphere?

Tectonic plates.

What is the asthenosphere and where is it situated?

The more fluid, partially molten (liquid) part of the upper mantle directly beneath the lithosphere where tectonic plates sit.

What dynamic process occurs within the asthenosphere that drives the movement of tectonic plates?

Convection currents.

What is the depth range of the Earth's lower mantle from the surface?

$610\,\text{km}$ to $2900\,\text{km}$.

How does the lower mantle differ in physical properties from the upper mantle?

It consists of partially molten rock that is hotter and denser than the upper mantle, and it does not flow like the upper mantle.

What is the chemical composition and state of matter of the Earth's outer core?

Molten (liquid) iron and nickel.

What is the depth boundary range of the Earth's outer core?

$2900\,\text{km}$ to $5150\,\text{km}$ (or $5100\,\text{km}$).

What planetary force is generated by the continuous movement of liquid iron and nickel in the outer core?

The Earth's magnetic field.

What is the composition and state of matter of the Earth's inner core?

Solid iron and nickel.

What depth range does the Earth's inner core span?

$5150\,\text{km}$ (or $5100\,\text{km}$) to approximately $6371\,\text{km}$ (or $6378\,\text{km}$) beneath the surface.

At what approximate depth below Earth's surface does the core-mantle boundary lie?

$2900\,\text{km}$.

According to the structural diagram of Earth, what is the distance from the surface to the Earth's center?

$6378\,\text{km}$ (or $6371\,\text{km}$).

What do the numerical depth markers $2900\,\text{km}$, $5100\,\text{km}$, and $6378\,\text{km}$ designate in this cross-section diagram?

The mantle-outer core boundary, the outer core-inner core boundary, and the center of the Earth.

Which specific layer of the Earth lies directly above the outer core?

The lower mantle.

What observation did cartographer Abraham Ortelius make in 1596 regarding global geography?

He noted that the coastlines of Africa and South America appeared to 'fit together'.

Who proposed the theory of 'Continental Drift' in 1912, and what did it assert?

Alfred Wegener; he theorized that the continents drifted apart from one another over millions of years.

Why was Alfred Wegener's theory of continental drift initially ridiculed by other scientists?

Because no one understood the physical mechanism or how continents could move through solid rock.

What mechanism did Arthur Holmes propose in 1927 to explain the movement of continents?

Convection currents operating within the mantle.

How does fluid move in a thermal convection current?

Hotter, less dense fluid rises; as it cools near the top, it becomes denser and sinks in a continuous cycle.

Which extinct land reptile provided fossil evidence connecting South America and Africa within Gondwana?

Cynognathus.

Across which separated continents were fossils of the terrestrial reptile Lystrosaurus found?

Africa, India, and Antarctica.

What small freshwater reptile provided fossil evidence linking South America and southern Africa?

Mesosaurus.

What extinct fossil fern was found across South America, Africa, India, Antarctica, and Australia?

Glossopteris.

What was Pangaea?

A historical supercontinent consisting of all Earth's landmasses joined together before breaking apart.

What is the typical density and rock composition of continental crust?

A density of approximately $2.7\,\text{g/cm}^3$, predominantly granitic in composition.

What is the typical density and rock composition of oceanic crust?

A density of approximately $2.9\,\text{g/cm}^3$, predominantly basaltic in composition.

How do continental crust and oceanic crust compare in thickness?

Continental crust is approximately $35\,\text{km}$ thick, while oceanic crust is approximately $7\,\text{km}$ thick.

What are the three ways tectonic plates can move relative to one another at their boundaries?

They can converge (collide into one another), diverge (move away from one another), or transform (slide horizontally past one another).

What occurs at a divergent plate boundary?

Plates pull apart or move away from one another.

What is seafloor spreading?

The process where new oceanic crust is created by magma rising at mid-ocean ridges, cooling, and pushing older crust away.

What geological landforms are formed by ocean-ocean convergent plate boundaries over millions of years?

Volcanic island chains or island arcs (such as the Japanese islands).

What process occurs when dense oceanic crust collides with less dense continental crust?

Subduction (the denser oceanic crust sinks beneath the buoyant continental crust into the mantle).

Why do volcanoes form inland from ocean-continent subduction zones?

As the oceanic plate subducts and sinks, it heats up, melts into magma, and rises to erupt violently through the continental crust.

What geological feature forms when two continental plates collide at a convergent boundary?

Huge mountain ranges (such as the Himalayas).

What occurs at a transform plate boundary?

Two plates slide horizontally past each other.

What is a fault in structural geology?

A fracture or break in the rock of the Earth's crust along which movement occurs due to immense stresses.

What famous transform fault line runs along the west coast of California in the United States?

The San Andreas Fault.

What prominent tectonic fault line is mapped here traversing western California?

The San Andreas Fault.

What is the Pacific Ring of Fire?

A major horseshoe-shaped zone of frequent earthquakes and active volcanoes surrounding the edges of the Pacific Ocean.

What tectonic boundary feature responsible for active volcanism is mapped in pink surrounding the Pacific Plate?

The Pacific Ring of Fire.

What movements in the Earth's crust cause earthquakes?

Tectonic plates converging, diverging, or sliding past each other, creating sudden releases of accumulated stress.

What is the focus of an earthquake?

The exact underground point where rock ruptures and the earthquake begins.

What is the epicentre of an earthquake?

The point on the Earth's surface directly vertically above the focus.

Where in the Earth's crust do minor tremors and earthquakes occur most frequently?

Wherever there is a weakness in the crust, particularly along faults.

What title is given to scientists who specialize in the study of earthquakes?

Seismologists.

What is a seismograph?

An instrument or machine used to detect and record seismic movements and tremors in the Earth.

What is a seismogram?

The paper chart or digital output record produced by a seismograph.

In what order do earthquake seismic waves arrive at a seismograph station?

Primary waves (P waves) arrive first, Secondary waves (S waves) arrive second, and surface waves arrive last.

How soon did the first P waves arrive on the example seismogram after the earthquake occurred at time $0$?

A little over $2\,\text{minutes}$ later.

When did the first S waves arrive on the sample seismogram relative to the earthquake's start time?

$4\,\text{minutes}$ later.

What critical distance metric does the S-P time interval provide to a seismologist?

It tells the seismologist how far away the earthquake's focus was from the recording station.

On this seismogram record, what seismic wave type arrives at marker 2 (just over $2\,\text{minutes}$)?

P wave (Primary wave).

Why do seismic surface waves arrive last at recording stations?

Because they travel the long way around the Earth's surface and move slower than internal body waves.

What physical parameter recorded on seismometers is used to determine earthquake magnitude?

The amplitude (height) of the seismic waves.

What standard logarithmic scale is most commonly used to measure the magnitude of an earthquake?

The Richter scale.

How is an earthquake with a Richter magnitude of $1.0$–$3.0$ described in terms of human perception?

Micro; only recorded locally, not felt except by very few people under especially favorable conditions.

What effects are associated with a Richter magnitude $4.0$–$4.9$ earthquake?

Light; felt indoors by many, outdoors by few; dishes and windows rattle; sensation like a heavy truck striking a building.

What structural consequences occur during a Richter magnitude $6.0$–$6.9$ earthquake?

Severe shaking; considerable damage in ordinary buildings with partial collapse; fall of chimneys, monuments, and walls.

What damage occurs in an earthquake measuring $7.0$ and higher on the Richter scale?

Violent to extreme destruction; most masonry and frame structures destroyed, bridges ruined, rails bent, and objects thrown into the air.

What magnitude on the Richter scale was the catastrophic 2004 Sumatra earthquake that triggered the Asian tsunami?

$9.1$.

What scale measures the localized shaking intensity and observed physical damage of an earthquake using Roman numerals I to XII?

The Modified Mercalli Intensity scale.

What damage description corresponds to Mercalli Intensity level XII?

Total damage; lines of sight and level are distorted, and objects are thrown upward into the air.

What two main factors determine the destructive power of an earthquake at any location?

Its distance from the epicentre and its magnitude (Richter scale value).

How does focal depth affect surface damage during an earthquake?

A larger but deeper earthquake may cause less surface damage than a smaller but shallower one.

Why do volcanoes typically form along oceanic-continental convergent plate boundaries?

The dense oceanic crust sinks, heats up, 'sweats' volatile fluids, and initiates melting of the mantle rock into rising magma.

What are the three operational stages used by scientists to categorize volcanoes?

Active, dormant, and extinct.

What defines an active volcano?

A volcano that has erupted recently and has the possibility of erupting again.

What defines a dormant volcano?

A volcano that has not erupted for a long time, but may still erupt in the future.

What defines an extinct volcano?

A volcano that erupted thousands of years ago and will probably never erupt again.

What subsurface pressure change causes a volcano to erupt?

Hot magma rises beneath the crust, increasing pressure until the surrounding rock fails and magma forces its way to the surface.

What is a volcano's magma chamber?

A large underground pool of liquid rock found beneath the surface of the Earth.

What is a volcanic conduit?

An underground pipe or passage through which magma travels upward toward the surface.

What is a volcanic vent?

An opening in the Earth's surface through which volcanic materials (magma, gases, ash) escape.

What is a volcanic crater?

The bowl-shaped mouth of a volcano that surrounds the central vent.

What is the throat of a volcano?

The uppermost entrance of a volcano that ejects lava and volcanic ash.

What is a side vent on a volcanic cone?

A secondary opening on the flank of a volcano where lava and gas can escape.

What is a volcanic ash cloud?

A cloud of fine pulverized rock and ash particles formed by explosive volcanic eruptions.

What volatile chemical compounds are prominently released in volcanic gas clouds?

Sulfur dioxide ($\text{SO}_2$) and water vapor ($\text{H}_2\text{O}$).

What is a volcanic sill?

A flat, horizontal sheet of igneous rock intruded between pre-existing horizontal rock layers.

What is volcanic ash fall?

The settling and deposition of airborne volcanic ash particles onto the landscape following an eruption.

According to this anatomical diagram, which structure is defined as 'an underground passage which magma travels through'?

Conduit.

What physiological metaphor describes how subducting plates release water to induce melting?

The plate gets hot enough to 'sweat' fluids.

In this classification guide, what category corresponds to a volcano that has erupted thousands of years ago and will probably never erupt again?

Extinct.

What thermodynamic event initiates the rise of magma toward a volcanic eruption according to this sequence?

Magma under the surface rises when it is hot, increasing subsurface pressure.

What is the scientific definition of a mineral?

Any naturally occurring solid substance with a definite chemical composition.

Name five common rock-forming minerals.

Feldspars, quartz, amphiboles, micas, and olivine (also garnet, calcite, pyroxenes).

What is the relationship between minerals and rocks?

Minerals are the chemical building blocks of rocks; rocks are aggregates of one or more minerals.

What three major minerals make up the rock granite?

Biotite (mica), feldspar, and quartz.

In which structural layer of the Earth do all rocks form?

The lithosphere (the crust and uppermost solid mantle).

Name two native chemical elements that occur naturally in pure crystalline form within rocks.

Diamonds (pure carbon) and gold.

In what combined chemical state are most metallic elements found in rocks?

Compounded with oxygen (oxides) or silicon (silicates).

What is the chemical formula of Potassium Feldspar?

$\text{KAlSi}_3\text{O}_8$.

What is the chemical composition formula of Plagioclase Feldspar?

$\text{NaAlSi}_3\text{O}_8 - \text{CaAl}_2\text{Si}_2\text{O}_8$.

What is the chemical formula of Calcite?

$\text{CaCO}_3$ (calcium carbonate).