Chapter 1 - Plate Tectonic

Cyclone book, junior cert/ junior cycle

Pangaea - definition

Large landmass of connected continents over 250 million years ago

Continental drift - meaning

Continents breaking apart and moving

Plate - definition

Large slab of earth’s crust

Plate boundary - definition

Where plates meet

Crust - definition

Thin outer layer of earth, made of solid rock

Mantle - definition

Magma found under the crust that moves in convection currents

Magma - definition

Hot molten and semi-molten rock

Outer core - definition

Molten and composed of nickel and iron

Inner core

Solid centre of earth with temperatures up to 6000 C

Continental crust - definition

Plates with land on top

Oceanic crust - definition

Crust with ocean on top

Convection currents - definition

Circular motion of magma within the mantle

How do convection currents work

1. Core heats magma above. Rises slowly towards crust

2. Magma rises, starts cooling

3. Cooled magma heavier sinks back towards core

4. Cycle repeats and causes convection currents

5. Causes slow colliding, separation and sliding movement of plates

Sliding boundaries - example

Transform boundary: Pacific and North American

Separating plates - example

Divergent - Eurasian and North American

Colliding Boundaries- example

Convergent boundaries - Eurasian and African

What happens when plates separate

Magma wells up to fill space between. Magma cools and forms new crust. Volcanic islands and mountains, mid ocean ridges formed

What happens when plates collide

Crust destroyed. Oceanic plate collides with continental, heavier oceanic forces under lighter continental into hot mantle. Part of oceanic melt and part of continental buckles. Forms fold and volcanic mountains

What happens when to plates slide

Edges sometimes lock together. Pressure builds up, an edge may snap/jolt suddenly. Great waves of energy released, causing trembling of earth as earthquake