Earth's Internal Structure
Crust - Mantle - Outer Core - Inner Core
CAPS Grade 10 Geography
Before you can understand tectonic plates, earthquakes, or volcanoes, you need a clear picture of the Earth's internal structure. This page breaks the planet into its main layers and shows why each one matters in Geography.
2,900 km
mantle thickness
5,000C
inner core temp
The Four Main Layers
| Layer | State | Thickness | Composition |
|---|---|---|---|
| Crust | Solid | 5-70 km | Silicates (rock) |
| Mantle | Semi-solid | ~2,900 km | Mg, Fe |
| Outer Core | Liquid | ~2,250 km | Molten Fe + Ni |
| Inner Core | Solid | ~1,220 km | Solid Fe + Ni |
Key Characteristics
Crust
SIAL (continental) - thicker, granite
SIMA (oceanic) - thinner, basalt
Mantle
Asthenosphere (semi-molten) - plates move.
Convection currents drive tectonics.
Convection currents drive tectonics.
Outer Core
Liquid iron-nickel - generates magnetic field.
Inner Core
Solid iron-nickel, >5,000C - immense pressure keeps it solid.
Important Terms
Lithosphere
Magma
Discontinuity
Moho
SIAL
SIMA
Asthenosphere
Convection
Moho: crust-mantle boundary. Lithosphere: crust + upper mantle.
Practice Games
six quick assessments - all reset buttons work
Quiz 1 - thickest layer?
A) Crust
B) Mantle
C) Outer core
D) Inner core
Quiz 2 - true/false
"Inner core is liquid"
True
False
Match
SIAL
continental
SIMA
oceanic
Asthenosphere
semi-molten mantle
Moho
crust-mantle boundary
Fill: magnetic field
Generated by ______ .
mantle
outer core
inner core
crust
Fill: discontinuity
Crust-mantle boundary = ______ .
lithosphere
Moho
core
asthenosphere
Order Outside to Inside
Crust
Mantle
Outer Core
Inner Core
Key Recap
A good exam answer should show how the crust, mantle, outer core, and inner core differ in state, thickness, and function. The mantle drives plate movement, and the outer core helps produce the Earth's magnetic field.
