Earth Science Quiz #2 Study - Lithosphere

Our planet is constantly evolving

True

What is the lithosphere?

The rigid, outer part of the Earth consisting of the crust and upper mantle

How thick is the crust?

5-100km

Is oceanic crust or continental crust more dense?

Oceanic crust

How thick is oceanic crust?

6-11km

How thick is continental crust?

25-70km

What is the composition of oceanic crust?

Mafic and ultramafic, basalt low in silica, melts into less viscous magma more common with effusive eruptions. Magnesium and iron-rich. 

What is the composition of continental crust?

Felsic, granite that is high in silica and less dense than oceanic. Melts into highly viscous magma that causes explosive eruptions. Silica and aluminum. 

How are mountains formed?

Tectonic plates or parts of plates are pushed together in convergent plate boundaries, pushed by sea floor spreading from plate divergence in mid-ocean ridges. 

What was used as evidence for the continental drift hypothesis?

Sea-floor fossils being found on continents far away from their natural areas. 

How are mid-ocean ridges formed?

Magma in the oceans rises and cools on the ocean floor, pushing old crust away.

What do mid-ocean ridges do to tectonic plates?

Moves them into other tectonic plates, creating subduction zones, earthquakes, and tsunamis. 

What is a hydrothermal vent?

An opening in the sea floor, heated mineral-rich water flows out and provides habitat for many extremist organisms in these superheated vents. 

What is paleo-magnetism?

The magnetic field direction was recorded with magnetite and points to the magnetic north at the time of its formation. How Earth’s magnetic field has changed and flipped throughout history. 

When lava cools, the crystals point north at that point in time. This is used for how we determine the history of the magnetic field shifting. 

True or False: Earth’s magnetic field reverses. 

True, it reverses and has done so many times without any measurable pattern. 

Is there a pattern for geomagnetic polarity reversing?

No, there is no pattern.

Where would you expect to find the newest lithospheric rock?

Next to mid-ocean ridges where new sea floor is being made.

What is a mantle plume?

A cylindrical upwelling of hot material from Earth’s interior. Hot, less dense material rises up to the surface and cools to creates islands and volcanoes. Also known as a stationary hotspot, which is how it created the chain of islands like Hawaii. It stays in the same place as the plates move. 

Are mantle plumes and stationary hotspots the same?

Yes, they are.

How was Iceland formed?

Iceland was formed through volcanic activity in the mid-Atlantic ocean ridge. As it separates, magma rises and creates the island. 

What is an earthquake?

The vibrations of the Earth produced by the rapid release of energy, energy is felt in the same way you break a slightly flexible stick. You bend and bend, and when it finally snaps, you feel the vibrations through both parts of the stick in your hands. 

What is a fault?

The fracture where one body of rock slides past another. The point on the stick that breaks. 

What is a normal fault?

A fault where the hanging and footwall are pulled apart and the footwall slides up and hanging wall slides down.

What is a reverse fault?

A fault where the hanging wall slides down and the footwall slides up because of compression.

What is a strike-slip fault?

Faults where rocks on either side move horizontally past each other. Two ships passing in the night and kinda rubbin on each other…

What are the cracks that run perpendicular to the mid-ocean ridges?

Oceanic strike slip faults, caused by divergent plate boundaries of the mid-ocean ridge not perfectly lining up 

What are the two types of geological waves?

P waves and S waves

S-Wave

Secondary seismic wave, does not have the energy/speed to pass through the Earth’s core

P-Wave

Primary seismic wave, has the energy to pass through the Earth’s core, but is slowed down and comes out at a different angle

What type of wave can go through the inner and outer core?

P-Wave

What are shadow zones?

Places on Earth during an earthquake where waves can’t be detected

What is the epicenter of an earthquake?

The surface directly above the center/focus point of the fault that caused the seismic rupture

Where are earthquake epicenters typically found?

Along subduction zones and mid-ocean ridges, lithospheric plate boundaries like the Ring of Fire

What are continental rifts?

Regions where the continental crust is being stretched and pulled apart, creating new ocean basins as it splits.

How do continental rifts create new ocean basins?

The continuation of a rift where the valley continues to widen and deepen until it drops below sea level and seawater floods in. This creates a narrow sea until it spreads and widens. 

How are mountain ranges formed that are not near fault lines?

Collisions from previous supercontinents, such as the Appalachians being in, Tennessee, Ireland, and other far away countries as they formed with an earlier supercontinent. Those plates converged and created the mountains, then split again later on into different plates. 

What eventually splits supercontinents?

Continent-continent divergent rifts - creates rift valleys that thin the crust until the new ocean basins form

What is a continental arc?

A chain of volcanoes in an arc formed by a subduction zone, often extremely tall, all within a line along the subduction zone

Island Arc

A string of islands formed by volcanoes along a deep ocean trench - Hawaii is an island arc formed by a stationary hotspot

Volcano

A vent through which molten rock erupts

Magma

Molten rock below the surface

Lava

Molten rock above the surface

Is all magma the same?

No, it can be made up of different minerals that change things like viscosity

Geotherm

A change in temperature with increasing depth 

Decompression melting

Melting of rock caused when a chunk of the lithosphere floats up and the pressure decreases, so it crosses the solid/liquid boundary line

How does decompression melting affect the crust of the Earth?

It creates new crust as it reaches the surface and cools

Flux-induced melting

Through subduction zones, water and CO2 are brought down into the mantle, which lowers the melting point of rock. The liquid/solid boundary itself changes 

Heat transfer melting

Heat from hot mantle magma transfers to cooler continental crust, causing the continental crust to melt

How are stationary hotspots formed?

Decompression melting causes the mantle plumes and causes volcanoes

Effusive eruption

Low viscosity magma from low silica content being melted like basalt makes the eruption continuous, with slow moving magma that consistently bubbles out. 

Explosive eruption

Explosive eruptions are caused by high viscosity magma that traps in gas and stores energy until it pops and creates an explosion, magma from melted granite and high silica content (felsic=high silica)

Mineral

A naturally occurring, inorganic solid with a crystalline structure and definite chemical composition

Rock

Naturally occurring solid mixture of one or more minerals or organic matter