U1 S5 Earth's Interior

What is the epicenter?

The place on Earth’s surface directly over the focus of an earthquake.

What is the focus?

The place deep inside Earth where a shift in Earth’s crust occurs, causing an earthquake.

What is the lithosphere?

A rigid layer composed of the crust and the upper mantle.

What is the asthenosphere?

The layer of the mantle on which the lithosphere floats.

What is the mantle?

The thick region between Earth’s core and crust.

What is the crust?

The outermost layer of Earth that forms Earth’s surface.

What are seismic waves?

Waves of energy that travel through Earth’s crust and interior.

What do geologists study?

The solid Earth, forces that shape it, rocks, minerals, and materials that form it.

What are two types of evidence used to study Earth's interior?

Direct evidence from core samples and indirect evidence from seismic waves.

What is a core sample?

A cylinder-shaped section of rock drilled out of the Earth, providing clues about its interior.

What are P waves?

Primary waves that move like a spring and travel through solids and liquids.

What are S waves?

Secondary waves that move like ripples in water and travel through solids only.

What are the three main layers of Earth?

Crust, mantle, and core.

How does temperature change with depth?

It increases with depth due to leftover heat from Earth's formation and radioactive substances in the core.

How does pressure change with depth?

It increases due to the weight of overlying rock pressing inward.

What is the crust made of?

Solid rock; continental crust is mostly granite, oceanic crust is mostly basalt.

How thick is the crust?

5–40 km thick, up to 70 km under mountains, thinner beneath oceans.

Differences between continental and oceanic crust?

Continental: granite, up to 70 km thick, less dense, older; Oceanic: basalt, 5–10 km thick, denser, younger.

What is the mantle’s depth and composition?

Starts ~40 km below surface, nearly 3,000 km thick, solid hot rock, denser than crust.

What are the three parts of the mantle?

Solid lithosphere, tarry asthenosphere, solid lower mantle.

What is the core made of?

Mostly iron and nickel.

How thick is the core?

3,486 km total; outer core 2,266 km thick, inner core 1,220 km thick.

What is the outer core like?

Molten metal that may create Earth's magnetic field.

What is the inner core like?

Solid metal.