structure of the earth Flashcards
What are the four main layers of the Earth?
inner core, outer core, mantle, and crust.
What is the inner core made of and how hot is it?
A solid layer of iron and nickel, with temperatures of 5000–6000°C.
How thick is the outer core and what state is it in?
Around 2100–2200 km thick and liquid/semi-molten.
What is the mantle and how thick is it?
A semi-molten layer about 2900 km thick, located between the crust and outer core.
What are the parts of the mantle?
The rigid upper mantle, the asthenosphere, and the lower mantle.
What is the asthenosphere?
A partially molten, plastic-like layer of the upper mantle that moves under high pressure.
What is the lithosphere?
The rigid upper part of the mantle plus the crust.
How thick is oceanic crust and what is it made of?
5–10 km thick and composed mainly of basalt.
What are the properties of oceanic crust?
Younger, thinner, denser, and is created and destroyed through plate movement.
How thick is continental crust and what is it made of?
25–100 km thick and made of granite.
What are the properties of continental crust?
Older, thicker, less dense, and not destroyed easily.
What causes convection currents in the mantle?
Heat from the Earth’s core, generated by radioactive decay.
What do convection currents do to tectonic plates?
They drag and move tectonic plates on top of the mantle.
describe constructive / divergent plate boundaries
plates move apart
what happens at divergent plate boundaries
Magma rises from the mantle to fill the gap.
It cools and solidifies, creating new oceanic crust.
Often forms mid-ocean ridges, volcanoes, and small earthquakes.
key features of divergent plate boundaries
Shield volcanoes
Volcanic islands
Frequent but gentle earthquakes and eruptions
describe destructive (convergent) plate boundaries
Denser oceanic plate subducts under the continental plate.
what occurs at destructive plate boundaries
Violent earthquakes
Explosive volcanoes
Deep ocean trenches
describe conservative plate boundaries
Sliding past each other at different speeds or directions , pressure builds up . pressure is suddenly released and causes an earthquake
what occurs at conservative plate boundaries
earthquakes
describe collision boundaries
🔹 No plate subducts — both are too light
🔹 Crust pushes upwards to form mountains
(between 2 continental plates)
