The Sea Floor

 Core – mostly iron  Inner core – solid  Outer core – liquid (temp. ~ 7,200° F)  Mantle – mostly solid, but it is so hot the rock is just about to melt. This allows the mantle to flow (magma)  Lithosphere – top part of upper mantle between mantle and crust  Asthenosphere – below Lithosphere

 Crust  Continental (mostly granite)  Oceanic (mostly basaltic rock, more dense)  The outer most layer  Up to 30 miles thick  2 kinds of crust  Oceanic (under oceans)  Continental (under continents)  Oldest is 3.8 billion years  The crust floats on the mantle and moves around

 The 1 st to propose Continental Drift Theory (1912)  At first was not widely accepted because: 1. He was a meteorologist not a geologist 2.Could not explain how continents drifted 3. Jigsaw puzzle model of continents had gaps  He named the super-continent “Pangaea”

 200 million years ago, Pangaea was surrounded by a giant ocean called “Pantalassa”  ~ 180 million years ago Pangaea began to drift apart  2 main continents were formed  Laurasia  Gondwana

Marine Biology 5 th Ed. Fig. 2.4 pg 25

 Used evidence to state the continents rested on large plates and drifted  Evidence used to support the theory includes:  Discovery of mid-ocean ridges (underwater mountain ranges)  Transform faults  Trenches  Magnetic Anomalies  Rifts  Fossils on the continental borders match up  Rock composition also matches up  Glacial Deposits  Sediment layers

Mid – Ocean Ridges

 New sea floor is made at the ridges  When the sea floor spreads, it creates rifts (cracks)  Lava flows out of the rifts and forms new sea floor  This is called sea floor spreading

The ship Glomar Challenger.

 Continental Drift and Seafloor Spreading Theories united  A dozen separate plates  Plates float on the asthenosphere  Plates are propelled by convection under the plate

 Where 2 plates meet is called a plate boundary (fault)  3 types of motions:  Divergent – 2 plates move apart  Creates mid-ocean ridges, mountains, islands and rift valley  Convergent – 2 plates collide  Creates trenches and island or volcanic arcs  Transform – 2 plates slide past each other  Creates earthquakes

Kobe Earthquake Japan, 1995

 If we realize the earth is moving, we can work backwards to see what it used to look like  Since the continents are still moving, 200 million years from today, the earth will look different from what we see now

 The deep sea floor averages ~13,000 ft deep  It is also called the Abyssal Plain  The abyssal plain is mostly flat with some mountains

-hot water around rift valleys and mid-ocean ridges which is heated by the hot magma -water carries high levels of hydrogen sulfide -Organisms such as clams, giant tubeworms, and crustaceans

An image generated with sonar of the President Jackson Seamounts in the Pacific Ocean 42º 30.60' N 127º 46.20' W

54º 34.80' N 150º 26.40' W

The End

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