The Earth’s Oceans and

Plate Tectonics Oceanography Unit #1

Our Earth Earth is between 5.0 and 7.0 billion years old. Crust Mantle Outer core Inner core

The Earth’s Crust Asthenosphere – an area of weakened crust

and molten upper mantle. Lithosphere – the rigid hardened crust.

Crustal types: Oceanic Crust – found beneath the ocean

basins Continental Crust – found beneath the

continents and margins

Crustal Comparsions

Earth’s Hydrosphere Oceans are approx. 4.0 billion years old. Oceans cover approx. 71% of the earth’s

surface.

Water? Oceans = 97.22% Glaciers = 2.15% Ground water = .62% Atmosphere, lakes, rivers, etc. = <.01%

The Ocean Basins

Southern Ocean – combination of the most southern Pacific, southern Atlantic, and southern Indian; surrounding Antarctica.

Ocean Topography Continental shelf – submerged edge of the continent;

most biologically active. Continental slope – descends from shelf down to the

deep sea-floor. Continental rise – sediments that accumulate at the

slope’s base. Abyssal plains – most of the ocean’s floor;

avg. depth = 4.0 km. Seamounts – submarine volcanoes Trenches – found at base of slope; depth >6.0 km.

Mid-Ocean Ridge System“Spreading centers”; crustal expansion.Largest geographical feature on planet.Total length is over 65,000 km.

Plate Boundaries1. Divergent:• Two or more plates are directed away from each other.• Mid-ocean ridge system• Numerous volcanic eruptions and earthquakes.• Volcanic islands such as Iceland, Azores, and Ascencion.

2. Lateral:• Two plates slip past each other.• San Andreas Fault (CA).• Numerous large earthquakes

Plate Boundaries1. Convergent:• Crustal plates are directed towards each other.

i. Two continental plates collide:• Build up of crust in to mountain ranges.• Himalayan Mountains

ii. One continental plate and one oceanic plate collide:• Creates subduction zones.• Japan Islands, New Zealand, Andes

Subduction Zone

Hotspots Areas where magma punches a hole in thin, weak

crust above; Stationary. Hawaiian-Emperor island chain: