Geology 12 Presents

Unit Outline Chp 10 Earth’s Interior Chp 11 Sea Floor Chp 12 Plate Tectonics Chp 9 Seismic (EQ) Chp 13 Structure

Chp 11 Seafloor Volcanoes outgasses water to fill oceans Average depth = 4 km Continental Margins mark edge of continent from deep sea floor 2 types of margins

1. Passive Margin = where oceanic plate is fused to continental plate and large amount of sediment is deposited. Ex: Eastern N. America Cont’l Margin Cont’l Plate Oceanic Plate Cont’l Shelf Cont’l Slope Cont’l Rise Abyssal Plain Submarine canyon fused

Cut into cont’l shelf-slope by: Submarine canyons Cut into cont’l shelf-slope by: a) rivers when sea-level was up to 130 m lower during ice ages animation b) turbidity currents = underwater landslides that erode slope and travel for 100’s of km Sediments are deposited as a deep sea fan as graded bedding

Passive Margins

Hudson River Submarine Canyon New York Cont’ shelf Hudson River Submarine Canyon Cont’ slope

2. Active Margin = where oceanic plate is subducting under continental plate Ex: W. coast of S. America Volcano Cont’l shelf Cont’l slope Trench Abyssal plain Cont’l plate Oceanic plate

Active Margins

Oceanic (spreading) Ridge: where new oceanic plate is being created by volcanism Island/seamount seamounts Rift valley Pillow lava Sheeted dikes and gabbro peridotite mantle

Ocean Ridge

Guyots New volcanic island Eroded flat by waves Guyot

Guyots & Seamounts

Guyots & Seamounts

Reefs Top view lagoon Fringing reef Cross section Barrier reef Atoll

Fringing Reef Island

Barrier Reef Island

Atoll

Islands get smaller as they age due to: a) wave erosion b) oceanic plate sinks as it moves way from divergent boundary or hot spot See Q14d, p.9 of WS 12.2

Use the diagram of a typical ocean basin to answer question 6. 6. The diagram represents a cross-section of an ocean basin. The number which represents a diverging plate boundary is A. 1 B. 2 C. 3 D. 4

Read Chapter 11 Do WS 11.1 Read Chapter 12 Go to Chp 12 Plate Tectonics