REVISION
1. Earth’s Layers (Like an
Onion!)
- Crust (Lithosphere):
The rocky outer layer.
- Continental Crust (SIAL):
- Made of granite (light
rocks: Silica + Alumina).
- Thicker (up to 30 miles under
mountains).
- Forms continents.
- Oceanic Crust (SIMA):
- Made of basalt (dense
rocks: Silica + Iron + Magnesium).
- Thinner (3-4 miles under oceans).
- Floats under continents like a dense
sea.
2. Mantle (Below the Crust)
- Thickness:
~1,800 miles.
- Composition:
Dense, hot rocks rich in olivine (a green mineral).
- Behavior:
Solid but can flow slowly over time (like thick toothpaste).
3. Core (Center of the Earth)
- Outer Core:
Liquid iron + nickel.
- Creates Earth’s magnetic field.
- Inner Core:
Solid iron + nickel.
- Temperature:
~3,500°F (hotter than lava!).
- Pressure:
So high it stays solid despite the heat.
Why Continents “Float”
- Lighter SIAL (continental
crust) floats on denser SIMA (oceanic crust), like ice in
water.
Hydrosphere & Atmosphere
- Hydrosphere:
All water (oceans, lakes, rivers) covering parts of the crust.
- Atmosphere:
Layer of gases (air) extending ~15 miles up.
How Do We Know This?
- Volcanoes:
Bring up mantle rocks.
- Earthquake Waves:
Speed changes reveal layers.
- Mining/Drilling:
Deep mines and drills sample the crust.
Fun Fact: If
Earth were an apple, the crust would be as thin as the apple’s skin! 🍎
Summary:
- Crust: Rocky surface
(continents + oceans).
- Mantle: Thick, hot
layer below.
- Core: Super-hot metal
center (liquid outer + solid inner).
- Continents float
on denser oceanic rock.
- Water (hydrosphere) and air (atmosphere)
wrap around the crust.