geology 12 presents. unit outline unit outline –chp 10 earth’s interior –chp 11 sea floor...

Geology 12Geology 12

PresentsPresents

Unit OutlineUnit Outline– Chp 10 Earth’s Chp 10 Earth’s

InteriorInterior– Chp 11 Sea FloorChp 11 Sea Floor– Chp 12 Plate Chp 12 Plate

TectonicsTectonics– Chp 9 Seismic Chp 9 Seismic

(EQ)(EQ)– Chp 13 StructureChp 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 PlateOceanic Plate

Cont’l Shelf Cont’l Slope Cont’l RiseAbyssal

PlainSubmarine canyon

Cont’l Margin

fused

• 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’

slope

Cont’ s

helf

2. Active Margin = where oceanic plate is subducting under continental plate

Ex: W. coast of S. America

Oceanic plate

Abyssal plain

Cont’l plate

Trench

Cont’l slope

Cont’l shelf Volcano

Active Margins

• Oceanic (spreading) Ridge: where new oceanic plate is being created by volcanism

Pillow lava

Sheeted dikes and gabbro

Rift valley

mantleperidotite

seamounts Island/seamount

Ocean Ridge

• Guyots

New volcanic island

Eroded flat by waves Guyot

Guyots & Seamounts

Guyots & Seamounts

• Reefs

Fringing reef

Barrier reef Atoll

Top view

Cross section

lagoon

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. 1B. 2C. 3D. 4

Read Chapter 11Do WS 11.1

Read Chapter 12

Go to Chp 12 Plate Tectonics