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Grade 7 SS [Geography] І www.notedsummaries.co.za
, Geologist
3 MAIN LAYERS CRUST = MOVES
HOW? (Plate tectonics)
Earth's crust = large puzzle pieces ( 7 tectonic plates) → on the mantle
→ plates move slowly = +- 1 to 10 cm p/year.
Moho
⊗ 🌋 Volcanoes → erupt when magma pushes
up at plate boundaries.
⊗ 🌍 Earthquakes → happen when plates
suddenly shift.
⊗ 🏔️ Mountains → form where plates press
Diameter → ± 12,700 km against each other (e.g. Himalayas).
DIVERGENT away from each other → new crust forms
→ Outer layer
CRUST → Thin(est) and hard → 5-70 km thick (like "new skin" at ocean floors).
→ Under sea = thin (ocean crust) → 10km Example: Mid-Atlantic Reef.
→ Under mountain = thick (continental crust) →35-70km
→ Moho = border between crust and the mantle Converging collide with each other → push and fold →
→ Middle layer = tough, warm + 2 900 km thick
MANTLE → Top part = hard
mountains or volcanoes
→ Lower part = soft and half-melted (magma) Example: Himalayan mountains.
→ Heat in mantle = convection currents (rock flows slow
→ causes plates to move) Transformative (move past each other)
→ 3,400 km thick Great tension builds on → sudden jerk =
CORE → Inner core = solid (very hot and under great pressure, earthquake.
2 5,000-6,000 °C).
nickel)7 SS [Geography] І www.notedsummaries.co.za
→ Outer core = liquid (iron andGrade Example: San Andreas Fault California.
Grade 7 SS [Geography] І www.notedsummaries.co.za
, Geologist
3 MAIN LAYERS CRUST = MOVES
HOW? (Plate tectonics)
Earth's crust = large puzzle pieces ( 7 tectonic plates) → on the mantle
→ plates move slowly = +- 1 to 10 cm p/year.
Moho
⊗ 🌋 Volcanoes → erupt when magma pushes
up at plate boundaries.
⊗ 🌍 Earthquakes → happen when plates
suddenly shift.
⊗ 🏔️ Mountains → form where plates press
Diameter → ± 12,700 km against each other (e.g. Himalayas).
DIVERGENT away from each other → new crust forms
→ Outer layer
CRUST → Thin(est) and hard → 5-70 km thick (like "new skin" at ocean floors).
→ Under sea = thin (ocean crust) → 10km Example: Mid-Atlantic Reef.
→ Under mountain = thick (continental crust) →35-70km
→ Moho = border between crust and the mantle Converging collide with each other → push and fold →
→ Middle layer = tough, warm + 2 900 km thick
MANTLE → Top part = hard
mountains or volcanoes
→ Lower part = soft and half-melted (magma) Example: Himalayan mountains.
→ Heat in mantle = convection currents (rock flows slow
→ causes plates to move) Transformative (move past each other)
→ 3,400 km thick Great tension builds on → sudden jerk =
CORE → Inner core = solid (very hot and under great pressure, earthquake.
2 5,000-6,000 °C).
nickel)7 SS [Geography] І www.notedsummaries.co.za
→ Outer core = liquid (iron andGrade Example: San Andreas Fault California.
