Tectonic Plates

Lithosphere

The rigid outer part of the earth (crust + upper mantle).

Asthenosphere

The semi-fluid layer below the lithosphere (plates float on this).

Subduction

Process of one plate sinking beneath another.

Trench

Deep depression in the ocean floor caused by subduction.

Mid-Ocean Ridge

Underwater mountain range at divergent boundaries.

Rift Valley

Lowland formed by divergent plates on land.

Volcanic Arc

A chain of volcanoes formed above a subducting plate.

Describe the movement of Divergent plates, and what landforms form.

Arrows Apart | Mid-Ocean Ridge, Rift Valley, New Crust | Mid-Atlantic Ridge, East African Rift.

Describe the movement of Transform plates, and what landforms form.

Arrows Sliding Past | Earthquakes, Faults (No volcanoes) | San Andreas Fault.

Conv (Cont-cont)

Arrows Together | Folded Mountains (No subduction/volcanoes) |

Himalayas.

Conv (Ocean-Ocean)

Arrows Together | Trench, Volcanic Island Arc | Japan, Aleutian

Islands.

Conv (Ocean-Cont)

Arrows Together | Trench, Volcanic Coastal Mountains | Andes,

Cascades.

Why are divergent boundaries often called “Constructive Boundaries”?

Because they create NEW crust (magma rises to fill the up)

Explain the age of rock at a mid-ocean ridge. Where is it youngest? Where is it oldest?

Youngest at the center (ridge), Oldest far away near the continents.

Divergent boundaries usually happen in the ocean. What is the specific name of the land feature formed when a divergent boundary happens on a continent (like in Africa)?

Rift Valley

Why are there no volcanoes at transform boundaries?

Because plates aren't separating (no magma rise) and not subducting (no melting).

What major natural disaster is most associated with transform boundaries?

Earthquakes

Explain what "Shearing" means in relation to rocks at this boundary.

Forces sliding in opposite directions, tearing the rock.

Density Rule: Which type of crust is denser: Oceanic or Continental? Why does this matter?

The ocean is denser. This matters because the denser plate always sinks (subducts).

Collision 1 (Cont-Cont): Why do the Himalayas have tall mountains but almost no volcanoes?

Both plates are too light/buoyant to sink, so they crumple up. No subduction = no melting = no volcanoes.

Collision 2 (Ocean-Ocean): When two oceanic plates collide, one subducts. Which one sinks, and what forms on the surface of the ocean?

The older/colder/denser one sinks. A Volcanic Island Arc forms.

Collision 3 (Ocean-Cont): Describe the process that formed the Andes Mountains in South America. (Use the words: Subduction, Trench, Magma, Volcanic Arc).

The dense Oceanic plate hits the Continental plate. The ocean plate Subducts creating a Trench. The plate melts, Magma rises, and creates a Volcanic Arc on land.

What is the "engine" driving all of this movement? Draw and label a picture to help you answer the question.

Convection Currents in the mantle.

What happens to the Earth’s crust at a transform boundary

Crust is neither created or destroyed

In millions of years, what is the likely fate of cities located on opposite sides of a transform boundary (like Los Angeles and San Francisco)?

They will slide past each other and eventually have different latitudes.

Why are volcanoes generally NOT found at transform boundaries?

Because there is no subduction or spreading to allow magma to reach the surface.

Which famous geological feature is located on a transform boundary between the North American Plate and the Pacific Plate?

The San Andreas Fault

How do tectonic plates move relative to each other at a transform boundary?​​​​​​​

The slide horizontally past each other

Convergent boundaries are often called "Destructive Boundaries." What is actually being destroyed?

The oceanic crust is being recycled back into the mantle.

Scenario: Oceanic-Continental Collision. An oceanic plate collides with a continental plate.  What is the inevitable result?

The oceanic plate will subduct (sink) beneath the continental plate, creating a trench.

Why do Continental-Continental collisions produce the tallest mountains in the world but almost NO volcanoes?

Because neither plate subducts, so they crumple upward instead of melting.

Scenario: Oceanic-Oceanic Collision. Two oceanic plates collide.  What feature forms on the surface of the less dense plate?

A Volcanic Island Arc

The Andes Mountains in South America are a classic "Continental Volcanic Arc." This means they were formed by:

An oceanic plate subducting beneath a continent, causing magma to rise through the land.

At a convergent boundary, which direction do the tectonic plates move?

Towards eachother

Divergent boundaries are often described as "Constructive Boundaries." What are they constructing?

New crust, as magma rises to fill the gap between plates.

At a divergent boundary, which direction are the tectonic plates moving?

Away from each other

When a divergent boundary occurs on land (like in Africa), what feature does it form?

A Rift Valley

If you were to take a submarine voyage starting at a Mid-Ocean Ridge (a divergent boundary) and traveled hundreds of miles away from it, what would you notice about the rocks on the seafloor?

The rocks get older and colder the further you go.

Which of the following creates the "force" that pulls the plates apart at a divergent boundary?

Convection currents in the mantle moving in opposite directions.