Earth's Interior

logo(1).gif (11000 bytes) A More Revealing Facts of the Earth
Earth's Interior

INTRODUCTION

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CORE

innermost part of the earth, partly solid, temp (2800 - 5000 degree C)

MANTLE

situated between the core & the crust, mainly solid rocks and magma, temp (2000 +++degree C)

CRUST

thin outermost layer of the Earth, solid rock which makes up the continents and the ocean floor.

TECTONIC PLATES

-pieces of the crust together with the upper part of the mantle.

MOVEMENT OF PLATES

Heat in the earth's interior causes the magma in the mantle to expand and rise. As the magma spreads out beneath the plates, the plates are dragged along and move away from each other. As the magma cools and sinks, plates are dragged towards each other. The repeated heating and rising of the magma sets up a continuous convection currents in the mantle causing the plates to move.

3 TYPES OF PLATE MOVEMENT

Divergent plates <plates moving away from each other>

As plates move apart, rocks break and form fracture in the crust. Earthquakes occurs along the plates boundary.Magma from the mantle rises through these fractures and solidifies, forming new crust. Divergent plates are considered constructive because new crust is formed causing the ocean floor to extend and increases in size (seafloor spreading). Oceanic ridge (long chain of Mts. on the ocean floor) also forms. E.g : Mid-Atlantic Ridge

Convergent plates <move toward each other>

When plates move towards each other, one plate is pushed downward beneath the other plate into the underlying mantle. This process is called subduction. Rocks also break and are displaced along the fracture (faulting), resulting in an earthquake. Along narrow deep depression forms at the subducted zone called an oceanic trench. Convergent plates are considered destructive as part of the subducted plate is destroyed. Fold Mountains and volcanoes also are being formed. E.g. : Java Trench

Plates Sliding Past Each Other

When When plates slide past each other, faulting occurs and earthquakes take place along the plate boundary. eg : San Andreas Fault (between Pacific plate and North American plate)

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