EPS 101 - SPRING 2003 Dr Adrian Brearley

Lecture 3 - Evolving Earth/Plate Tectonics

Keywords and concepts

Evolving Earth

Planetary Differentiation – process of conversion of nebular materials into a planet with a core, mantle and crust.

Heating mechanism – impact heating, decay of radioactive elements

Melting of the Earth – formation of magmas (melted rocks).

Crust - thin solid outer layer of the Earth up to 40 km thick – composed of light elements that floated to the top of the molten earth – main elements present are oxygen (O), silicon (Si), aluminum (Al), iron (Fe), magnesium (Mg), calcium (Ca), potassium (K), sodium (Na).

Mantle – below crust – 40-2891 km depth. Makes up bulk of solid earth. Rocks of intermediate density, made up mainly of Si, Mg, Fe, and O.

Core – central, interior zone of the Earth made of iron (Fe), consists of outer and inner core – outer core extends from 2891 to 5150 km and is liquid, inner core extends from 5150 to 6370 km (center of the Earth).

Formation of continents, oceans and atmosphere. Cooling of molten earth, solidification of crust, mantle. Loss of volatile elements (hydrogen (H), nitrogen (N), water (H₂O), carbon dioxide (CO₂)) to form atmosphere and oceans.

Plate tectonics

Plate tectonics – theory that the Earth’s geological behavior is controlled by the formation, movement, interaction and destruction of large rigid plates on the surface of the Earth.

Lithosphere – cooler, rigid crust and upper part of mantle.

Asthenosphere – below lithosphere – hotter, weaker zone below lithosphere.

Convection – heat transfer that drives movement of material in the mantle.

Plate boundaries – divergent, convergent, transform fault boundaries.

Mid-ocean ridges – places where plates move apart and new oceanic crust is formed from upwelling of magma.

Subduction zone – Boundary between converging plates where one plate sinks below the other and is recycled into mantle.

Seafloor spreading – Widening of oceanic basins due to separation of plates and formation of new oceanic crust by upwelling of magma at the boundary between the plates.

Continental drift – theory that continents embedded within lithospheric have drifted with geological time over the surface of the Earth.