INTRO TO MARINE SCIENCE - Lecture 4

Seafloor Provinces

Continental Shelf

• nearly flat edge of submerged continents

• very gentle slope towards ocean basin

• formed by trapping of land sediments

Continental Slope

• edge of shelf (shelf break)

• steeper slop extending into ocean basin

• can be devoid of sediments depending on steepness

• submarine canyons — extensions of rivers carved during last low sea

Continental Rise

• transition from slope to deep ocean floor

• gentle slope formed by sediment accumulation

• sediments delivered by turbidity currents and underwater landslides

Abyssal Plains

• covers 30% of Earth’s surface; largest ecosystem

• formed by burial of irregular topography

Abyssal Hill

occur where sediment is not thick enough to cover under rock

• usually extinct volcanoes and found running parallel to mid ocean ridges

Seamounts

steep sided underwater volcano (small rounded top)

Guyots

drowned volcanic islands that did not become coral atolls

• planed flat by wave action at shallow depths and subsequent subsidence

Hotspots

areas of isolated volcanic activity

• center of plates (continental and oceanic)

• mid ocean ridges

• intense areas of earthquake activities

What do hotspots do?

• periodically move material from as deep as mantle core boundary

• Form volcanic islands and seamounts when they penetrate the lithosphere

• form giant swells in ocean or crust when they fail to break through lithosphere

  • Yellowstone

What are some examples of Seamount Chains?

• Hawaiian. Island - emperor seamount chain

• Tuamotu Archipelago - line island chains

• Austral, Gilbert and Marshall Island chains

Seamount Chains

approximately parallel and could have been formed by the same motion of the Pacific plate over 3 hotspots