science chapter 3 tectonic plate

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What is plate tectonics?

The theory that Earth's crust is broken into moving tectonic plates.

What is a tectonic plate?

A large, rigid piece of Earth's crust and upper mantle.

What causes tectonic plates to move?

Convection currents in the mantle, ridge push, and slab pull.

What are convection currents?

The movement of hot mantle rock rising, cooling, and sinking.

What is a divergent boundary?

A boundary where two tectonic plates move apart.

What happens at a divergent boundary?

New crust forms through sea-floor spreading.

What is a convergent boundary?

A boundary where two tectonic plates move towards each other.

What can happen at a convergent boundary?

Subduction, mountain building, volcanoes, and earthquakes.

What is a transform boundary?

A boundary where two tectonic plates slide past each other.

What natural hazard is common at transform boundaries?

Earthquakes.

What is subduction?

The process where a denser tectonic plate sinks beneath another plate.

Which plate usually subducts?

The oceanic plate because it is denser.

Why doesn't continental crust usually subduct?

It is less dense and more buoyant than oceanic crust.

What is sea-floor spreading?

The process where new oceanic crust forms at mid-ocean ridges.

Where does sea-floor spreading occur?

At divergent plate boundaries.

What is ridge push?

The force pushing plates away from a mid-ocean ridge as new crust forms.

What is slab pull?

The force created when a sinking plate pulls the rest of the plate.

Who proposed continental drift?

Alfred Wegener.

What is continental drift?

The idea that continents were once joined and slowly moved apart.

What was Pangaea?

A supercontinent that existed before breaking apart into today's continents.

What evidence did Wegener use for continental drift?

Matching coastlines, fossils, rock formations, mountain ranges, and ancient climate evidence.

What is oceanic crust?

Thin, dense crust beneath the oceans.

What is continental crust?

Thicker, less dense crust that forms the continents.

Why is oceanic crust denser than continental crust?

It is made mainly of basalt, while continental crust is mainly granite.

Why do most earthquakes occur at plate boundaries?

Because plates collide, separate, or slide past each other.

What causes a tsunami?

A large undersea earthquake that displaces water.

What causes volcanoes?

Magma reaching Earth's surface, often near convergent or divergent boundaries.

What is magma?

Molten rock beneath Earth's surface.

What is lava?

Magma after it reaches Earth's surface.

What are the four layers of the Earth?

Crust, Mantle, Outer Core, Inner Core.

Which layer of the Earth is the thinnest?

The crust.

Which layer of the Earth is the thickest?

The mantle.

Which layer of the Earth is liquid?

The outer core.

Which layer of the Earth is solid and hottest?

The inner core.

How fast do tectonic plates move?

A few centimetres each year.

Why is the Mid-Atlantic Ridge important?

It is evidence of sea-floor spreading where new crust is created.

How does sea-floor spreading support plate tectonics?

New crust forms at ridges and pushes older crust away.

How did the Himalayas form?

When the Indian Plate collided with the Eurasian Plate.

What happens when two continental plates collide?

They form mountain ranges because neither plate easily subducts.

What happens when an oceanic plate collides with a continental plate?

The oceanic plate subducts beneath the continental plate.

Why is GPS useful in studying plate tectonics?

It measures the movement of tectonic plates very accurately.

What features can form when Australia collides with Indonesia?

Mountains, volcanoes, and more earthquakes.

How can plate movement affect climate?

Mountains change rainfall patterns and volcanoes can temporarily cool the climate.

What is the difference between magma and lava?

Magma is underground; lava is on the Earth's surface.

What is the difference between oceanic and continental crust?

Oceanic crust is thinner and denser; continental crust is thicker and less dense.

What is the difference between divergent and convergent boundaries?

Divergent plates move apart; convergent plates move together.

What is the difference between convergent and transform boundaries?

Convergent plates collide; transform plates slide past each other.

What is the central part of the Earth called?

The core.