1 Earth’s Formation and Internal Structure Free Online FlashCards

What makes Earth a system?

A system is a set of parts that interact and exchange matter and energy.

How old is Earth, and what evidence helps estimate its age?

Earth formed about 4.54 billion years ago. Scientists estimate its age mainly by radiometric dating and comparison with meteorites.

What are Earth’s three compositional layers?

The crust is the thin, solid outer layer; the mantle is hot, mostly solid silicate rock; and the core is the dense, mainly iron-rich center.

What is the lithosphere made of?

The lithosphere is the rigid outer shell made of the crust and uppermost mantle; it is broken into tectonic plates.

How do the physical states of Earth’s outer and inner cores differ?

The outer core is liquid, while the inner core is solid. Immense pressure keeps the extremely hot inner core from melting.

How do P and S waves help reveal the outer core’s state?

P waves travel through solids and liquids, but S waves travel through solids only. The absence of S waves passing through the outer core is key evidence that it is liquid.

What two energy sources power Earth-system processes?

Earth-system processes are powered by energy from the Sun and heat from Earth’s interior.

How did early Earth form and heat up?

Dust and rocky material orbiting the young Sun gradually clumped together under gravity. Collisions, compression, and radioactive decay heated the growing planet.

What happened during Earth’s differentiation?

Dense, iron-rich material sank toward the center, while lighter rocky material rose, forming Earth’s core, mantle, and crust.

How did the early atmosphere and oceans develop?

Volcanic gases from Earth’s interior contributed to the early atmosphere. As Earth cooled, water vapor condensed and helped form oceans.

Which is generally thinner: oceanic or continental crust?

Oceanic crust is generally thinner than continental crust.

How can mantle rock flow if the mantle is mostly solid?

The mantle is mostly solid, but its rock can deform and flow very slowly over geologic time.