The Sea Floor

Layers of the Earth

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

Layers of the Earth (con’t.)

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

Alfred Wegner The 1st 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”

Continental Drift & the Changing Ocean

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 5th Ed.Fig. 2.4 pg 25

Seafloor Spreading Theory 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

Creation of the Sea Floor

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.

Theory of Plate Tectonics

Continental Drift and Seafloor Spreading Theories united

A dozen separate plates Plates float on the asthenosphere Plates are propelled by convection under

the plate

Plate Tectonics 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

Geologic History of the Earth

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

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

Characteristics of Hydrothermal Vents:

-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 thePacific Ocean42º 30.60' N 127º 46.20' W

54º 34.80' N 150º 26.40' W

The End

Pangaea of Not?

Rubric

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