Today’s Plan Ocean floor topography Continental Margins Turbidity Currents Atolls Mid-ocean ridges Ocean crust

WarmUp answers - cool MOR stuff the pressure is strong enough to crush any man-made vessel like a puny grape between the fingers of Andre the Giant. Before visiting this site I did not know that Iceland is located on a hot spot on a mid- ocean ridge. I thought it was that in a hundred years, only 6m of new crust at mid-ocean ridges forms.

WarmUp answers - cool MOR stuff That it is not all connected as one. I had the idea that it was one long segment, but it is actually broken into segments. I learned that tube worms will frequently colonize on new and old lava.When they do this, they form a base for the "hydrothermal vents" on the lava flow.

Where is the flattest place on earth? 1.Kansas 2.Tibetan Plateau 3.Abyssal Plains 4.South Pole

Book image is exaggerated Abyssal Plains have slopes of around 1:10,000

Active Continental Margins What does an active margin look like? How does it relate to plate tectonics?

Active Continental Margin What is this?

Passive Continental Margins What does a passive margin look like? How does it relate to plate tectonics?

Passive Continental Margin What is this?

Turbidity Currents Like mudflows: dense, fast-moving, powerful discovered in 1929 –Grand Banks quake –turbidity current broke 13 transatlantic telegraph cables –timing of breaks indicates speed > 50 mph –current extended > 500 miles from source

Turbidity Current Modeling

Turbidites

Seamounts, Reefs, Atolls Important for Hot Spot theory Corals live in shallow water, but make huge kms- high mountains (seamounts) in open ocean - how?

Mid-ocean ridges Oceanic crust structure is formed at MORs –called ophiolite when it’s on land

Pillow Basalt - Rosario Head

Pillows Top of Pillow Basalt Fault Chert (weakly metamorphosed diatomaceous earth)

Mid-ocean ridges Chert is deposited on top

Why ridges at spreading centers? Sediment blankets new ocean floor, so why isn’t the rift area a valley? Heat  thermal expansion

Seafloor spreading

Movement of Continents Continental Drift: from theory to explanation Harry Hammond Hess: mantle convection and sea floor spreading

TECTONICS Seafloor –Thin veneer of sediments –Basalt (lava rock) Magnetized to earth’s magnetic field when it cools below 600 degrees C. –Normal polarity –Reverse polarity

Paleomagnetism

Seafloor –Basalt (lava rock) Is magnetized to earth’s magnetic field when it cools below 600 degrees C. –Normal polarity –Reverse polarity North is not always the dominant pole on Earth TECTONICS

The Geomagnetic Reversal Time Scale

TECTONICS Seafloor spreading –The mechanism for continental drift –Proved by seafloor mapping Alternating linear regions of normal and reversed polarized seafloor

Discovery of Sea-Floor Spreading Alternating linear regions of normal and reversed polarized seafloor

TECTONICS Seafloor spreading –Alternating linear regions of normal and reversed polarized seafloor

TECTONICS Seafloor spreading –A mechanism for plate tectonics

MOR Hydrothermal System recharge (infiltration) heat & absorb ions rise black smoker - ions form tiny mineral grains as water cools

Black Smokers