4B1 Tectonics and Internal Earth Processes Flashcards
Describe how plate tectonics drives Earth's crustal movements, forming features like mountains and volcanoes and providing insights into Earth's interior structure and magnetic field.
What are the 4 layers of the Earth?
- The Inner Core
- The Outer Core
- The Mantle
- The Crust
What is the lithosphere?
The rigid outer layer of Earth, including the crust and upper mantle.
The lithosphere is broken into tectonic plates that interact at boundaries.
Define:
plate tectonics theory
It explains that Earth’s lithosphere is divided into plates that move over the asthenosphere.
This theory unifies ideas of continental drift and seafloor spreading, describing the motion of tectonic plates caused by forces within the Earth.
What is the average thickness of the lithosphere?
About 100 km.
Oceanic lithosphere ranges from 5–100 km in thickness, while continental lithosphere varies from 40 km to over 200 km in ancient regions.
What are two primary driving forces of plate motion?
- Slab pull
- Ridge push
Slab pull is caused by the sinking of a dense plate into the mantle; ridge push results from gravitational forces at mid-ocean ridges.
Fill in the blank:
The movement of tectonic plates is primarily driven by ________ currents in the mantle.
convection
Heat from Earth’s core causes mantle material to rise and sink, creating convection currents that drive plate motion.
What is slab pull?
The force exerted by a sinking, subducting plate.
This force occurs as the dense oceanic plate sinks into the mantle at subduction zones, pulling the rest of the plate with it.
What is ridge push?
The gravity-driven force on the raised lithosphere at mid-ocean ridges.
Newly formed, warm crust at ridges is less dense and slides away due to gravity, pushing older crust outward.
What are the three main types of plate boundaries?
- Convergent
- Divergent
- Transform
These boundaries describe the interactions between tectonic plates, such as collision, separation, and lateral sliding.
What happens at a convergent boundary?
Two plates collide, and one may subduct beneath the other.
Convergent boundaries can form mountain ranges, trenches, or volcanic arcs, depending on the plates involved.
Fill in the blank:
A ________ boundary occurs when two tectonic plates move apart.
divergent
Divergent boundaries often create mid-ocean ridges or rift valleys.
What happens at a transform boundary?
Two plates slide past each other horizontally.
Transform boundaries are associated with strike-slip faults, such as the San Andreas Fault in California.
True or False:
Subduction occurs at divergent boundaries.
False
Subduction occurs at convergent boundaries where one plate sinks beneath another.
What geological feature provides evidence for seafloor spreading?
Mid-ocean ridges
These ridges form where magma rises to create new crust, pushing older crust outward.
Fill in the blank:
The presence of ________ fossils on separate continents supports the idea of continental drift.
identical
Fossils of species like Mesosaurus found on continents now separated by oceans suggest they were once connected.
How does seismic activity provide evidence for plate tectonics?
Earthquakes happen at plate boundaries, showing plate interaction.
The distribution of seismic activity aligns with the edges of tectonic plates.
True or False:
Volcanoes only occur at convergent plate boundaries.
False
Volcanoes also occur at divergent boundaries (e.g., mid-ocean ridges) and hotspots.
Which type of plate boundary is the San Andreas Fault?
Transform
The San Andreas Fault is an example of a strike-slip fault where the Pacific Plate slides past the North American Plate.
What is formed when two continental plates collide?
Mountain ranges
The Himalayas are an example of mountains formed at a convergent boundary between two continental plates.
True or False:
Tectonic plates are made only of continental crust.
False
Plates can consist of both oceanic and continental crust, or just one type.
Fill in the blank:
The ________ is the name of the supercontinent that existed about 300 million years ago.
Pangaea
Pangaea eventually split apart due to tectonic plate movements, forming the continents we know today.
What is crustal deformation?
The bending, stretching, or compression of Earth’s crust.
Deformation can result from stress caused by plate movements, leading to features such as folds, faults, and fractures.
What are the three types of stress that cause deformation?
- Compression
- Tension
- Shear
Compression squeezes rocks, tension stretches them, and shear stress causes sliding in opposite directions.
Fill in the blank:
Deformation typically occurs in Earth’s _________.
lithosphere
The lithosphere is rigid and can deform under tectonic forces, leading to geological features.
What is folding?
Bending of rock layers.
Folds often form in sedimentary rocks and create features like anticlines and synclines.
What is faulting?
Breaking of rock layers with movement.
Faults are classified as normal, reverse, or strike-slip based on the direction of movement.
True or False:
Faulting occurs without breaking the rock.
False
Faulting involves the breaking of rocks, often leading to earthquakes.
Fill in the blank:
________ deformation results in permanent changes to the shape of rocks.
Plastic
Plastic deformation occurs under high pressure and temperature, causing rocks to bend rather than break.
What is brittle deformation?
Breaking of rocks under stress.
Brittle deformation typically occurs near Earth’s surface where temperatures and pressures are lower.
What type of plate boundary is associated with trenches?
Convergent
Trenches form at subduction zones, where one tectonic plate is forced beneath another, typically involving an oceanic plate descending into the mantle, creating deep underwater depressions.
True or False:
Trenches can form at transform boundaries.
False
Trenches are exclusive to convergent boundaries where subduction occurs.
Fill in the blank:
Volcanic mountains form when ________ builds up.
magma
Volcanic mountains are often found at convergent and divergent plate boundaries.
How are earthquakes related to deformation?
They release energy when rocks shift.
Earthquakes usually happen at plate boundaries where stress accumulates.
What are seismic waves?
Waves of energy that travel through Earth’s layers.
They are generated by earthquakes and provide insight into Earth’s internal structure.
Fill in the blank:
The point on Earth’s surface directly above the earthquake’s focus is called the __________.
epicenter
The epicenter is the point on Earth’s surface directly above the earthquake’s focus (hypocenter), where seismic waves typically cause the greatest shaking and damage.
Where are most earthquakes located?
Along tectonic plate boundaries.
Earthquakes frequently occur in regions where plates collide, pull apart, or slide past each other.
True or False:
Earthquakes are equally distributed around the world.
False
Earthquakes are concentrated along plate boundaries, forming the Ring of Fire around the Pacific Ocean.
What is the measure of energy released during an earthquake?
Magnitude
Magnitude is commonly measured using the Richter scale or moment magnitude scale (Mw).
True or False:
The Richter scale measures the damage caused by an earthquake.
False
The Richter scale measures the earthquake’s size, not the damage. The damage is often measured by the Modified Mercalli Intensity scale.
What is the moment magnitude scale?
A scale that measures the total energy released by an earthquake.
It is more accurate than the Richter scale for large earthquakes, considering the fault size and slip.
Fill in the blank:
A magnitude 7 earthquake is _____ times more powerful than a magnitude 6 earthquake.
32
Each whole number increase on the magnitude scale represents a 32-fold increase in energy release.
What are P-waves?
Primary waves that are the fastest seismic waves.
P-waves travel through both solids and liquids, causing particles to move back and forth.
What are S-waves?
Secondary waves that are slower than P-waves.
S-waves move through solids only, causing particles to move in a side-to-side motion.
Fill in the blank:
_____ waves cannot travel through liquids.
S-waves
S-waves are stopped by the Earth’s outer core, which is liquid, helping scientists study Earth’s interior.
What wave causes the most damage during an earthquake?
Surface waves
Surface waves, including Love and Rayleigh waves, move slower than P-waves and S-waves but have larger amplitudes, causing intense ground motion that leads to significant structural damage.
True or False:
Seismic waves travel faster through less dense materials.
False
Seismic waves travel slower through less dense materials and faster through denser materials.
What are aftershocks?
Smaller tremors that occur after the main earthquake.
Aftershocks happen as the Earth adjusts to the new position of the tectonic plates.
What is a seismograph?
An instrument used to detect and record seismic waves.
Seismographs measure the ground motion caused by earthquakes and provide data about their intensity and duration.
True or False:
Aftershocks are usually stronger than the main earthquake.
False
Aftershocks are smaller, but they can still cause significant damage.
What is a volcano?
A rupture in Earth’s crust where molten lava, gas, and ash escape.
Volcanic eruptions occur when magma from Earth’s mantle reaches the surface, forming lava, ash, and gases.
Fill in the blank:
The largest type of volcano is a _______ ________.
shield volcano
Shield volcanoes can cover large areas with lava flows, making them the largest by volume and area.
What causes volcanic eruptions?
Pressure from magma forces its way through Earth’s crust.
Magma rises due to pressure from tectonic plate movements or hot spots, leading to eruptions.
True or False:
Composite volcanoes have gentle eruptions.
False
Composite volcanoes tend to have explosive eruptions due to the thick, viscous magma that traps gas.
What is the difference between a shield and a composite volcano?
- Shield volcanoes have gentle slopes.
- Composite volcanoes are steeper and more explosive.
Shield volcanoes produce fluid lava, while composite volcanoes alternate between lava flows and explosive eruptions.
Fill in the blank:
The _____ ___ _____ is a major area in the Pacific Ocean where many earthquakes and volcanoes occur.
Ring of Fire
This region encircles the Pacific plate and is home to 75% of the world’s active volcanoes.
What is magma?
Molten rock beneath Earth’s surface.
When magma reaches the surface, it is called lava, and its composition affects the type of eruption.
What is magma called when it reaches Earth’s surface?
Lava
Lava cools and solidifies, forming rocks such as basalt or andesite.
True or False:
Lava that is high in silica tends to flow more quickly.
False
Lava high in silica is more viscous, causing it to flow slowly and often form steeper volcanic cones.
What is a hotspot?
A volcanic region fed by mantle plumes beneath a tectonic plate.
Examples include the Hawaiian Islands, which formed as the Pacific Plate moved over a hotspot.
How do hot spots form volcanoes?
By magma rising from deep within the Earth.
As tectonic plates move over hot spots, a series of volcanoes can form, like the Hawaiian chain.
What is pyroclastic flow?
A fast-moving mixture of hot gas, ash, and volcanic material.
Pyroclastic flows are extremely dangerous, as they travel quickly and can reach temperatures of over 1,000°C.
True or False:
Volcanic eruptions always lead to significant damage.
False
While eruptions can be catastrophic, many eruptions, especially from shield volcanoes, are non-explosive and cause minimal damage.
Fill in the blank:
Volcanic _____ is fine particles of rock and mineral debris ejected during an eruption.
ash
Ash can cause health problems, disrupt air travel, and damage buildings and crops.
What is the Earth’s crust made of?
Solid rock, including silicates like basalt and granite.
The crust is Earth’s outermost layer and is composed of continental (granite) and oceanic (basalt) rocks.
Fill in the blank:
The mantle consists mostly of silicate minerals rich in ________ and ______.
magnesium; iron
The mantle is composed of semi-solid rock that is more viscous than the crust, extending to about 2,900 km deep.
True or False:
The Earth’s crust is the thickest layer.
False
The crust is the thinnest layer, averaging 5–70 km in thickness, whereas the mantle is ~2,900 km thick, and the core (outer + inner) is ~3,500 km thick.
Which layer of Earth is composed of liquid iron and nickel?
The outer core.
The outer core is liquid due to the high temperatures but remains in motion, generating Earth’s magnetic field.
True or False:
The inner core is composed of solid iron and nickel.
True
The high pressure at the Earth’s center keeps the inner core solid, despite its extreme temperature.
Which layer is the thickest?
The mantle.
The mantle makes up about 84% of Earth’s total volume.
How does the temperature of the inner core compare to the outer core?
The inner core is hotter.
The inner core’s temperature can reach up to 5,500°C, hotter than the outer core, but it remains solid due to immense pressure.
How deep does the Earth’s mantle extend?
2,900 km
The mantle lies between the Earth’s crust and the outer core, extending to significant depths.
Fill in the blank:
The Earth’s ______ _____ is primarily responsible for generating Earth’s magnetic field.
outer core
The movement of molten iron and nickel in the outer core generates the geodynamo effect, which creates Earth’s magnetic field.
What is the Van Allen radiation belt?
A layer of charged particles trapped by Earth’s magnetic field.
These belts protect Earth from harmful solar and cosmic radiation by trapping and redirecting the particles.
True or False:
Earth’s magnetic field is strongest near the equator.
False
The magnetic field is strongest at the poles, where the field lines converge.
What is the geodynamo?
The process by which Earth’s magnetic field is generated.
The geodynamo arises from the convective movement of molten metal in the outer core, creating an electrical current.
Fill in the blank:
The Earth’s magnetic field helps protect us from harmful ______ ________.
solar radiation
The magnetic field acts as a shield, deflecting harmful solar and cosmic radiation.
What is a geomagnetic reversal?
A reversal of Earth’s magnetic poles.
Geomagnetic reversals have occurred throughout Earth’s history, where the magnetic north and south poles switch places. These reversals leave fossil evidence with “magnetic stripes” in rock.
This evidence helps support the theory of plate tectonics, as scientists can use the stripes to estimate the rate of movement of plates over time.
