the sea floor. distribution of the worlds ocean 71% of the earth is covered by water. four large...
TRANSCRIPT
The Sea Floor
Distribution of the Worlds Ocean
71% of the earth is covered by water.Four large basins
Pacific, Atlantic, Indian, Arctic.
Southern hemisphere is 80% ocean while Northern hemisphere is only 60% ocean.
Separate by connected basins
Include features like….
Most of the ocean bottom is an abyssal plain
Have you ever wonder why our planet has oceans? The theory of plate tectonics can explain the presence and features of the ocean basins on our planet…
The Sea Floor
Geology: Study of the development and physical characteristics of the planets sea floor and continents and the forces that shape them.
How did oceans and continents form?
Big Bang Theory
15 Billion years ago
Matter expanded into space.
Earth and Solar system originated from a cloud or clouds of dust.
Dust particles collided with each other – those larger particles collided with one another – then those larger particles collided with one another, and so on…
Formation Of Layers
HeatingDenser (Fe and Ni) material sunk to the center. Lighter (Si and O) material rose to the surface. Some materials vaporized to form early oceans and atmosphere.
Layers Form
Planet Cools
Image of Earth
Early Atmosphere• Water vapor, carbon monoxide, hydrogen
sulfide, nitrogen and cyanide
• 4 bya water vapor from mantle is cooled and collects on surface.
• 1000’s of years of thunderstorms and rain
• Low lying spots fill to become our early oceans
• Water also from comets, volcanoes, meteors, geysers, rocks that contain moisture
Origin Of Continents
Alfred Wegher suggested the continents were not always on their present positions.
Continental Drift
200 mya, A single landmass called Pangea broke up.
Evidence…
Coastlines fit like a puzzle.
Similar fossils and rock formations on different continents.
Problems with CD• No mechanism for how the
continents “drift”• Wegener was a meteorologist…what
did he know anyway!!!
CRUST – thin outer layer
•less dense, rocks that floated to the surface when the Earth was formed
• between 35km and 70km thick. – not a continuous layer of rock
• Split into plates, which are free to drift slowly across the surface of the planet.
Moving Plates
Continents move 1cm/yr
Boundary between plates is a FAULTSeismic activity occurs at faults
The lower mantle is heated by the core which creates convection currents.
Rising magma may break thru the crust at ridges…. i.e. mid-atlantic ridge.
Moving Plates
Spreading sea floor –plates move apart from rising magma ridge
Subduction – Two plates collide and the denser plate sinks into the mantle
Forms trenches.
Ocean Floor Formation
Sea floor spreading is the source for new ocean floor.
Subduction recycles ocean floor back into the mantle
Subduction and Trenches
Sea Floor Evidence
Young rocks are found closer to the ridge.
Less sediment closer to the ridge
Magnetic bandsMinerals line up as magma cools with N pole.
N and S pole flip periodically.
Plate Tectonics
Unifying theory that combines continental drift and sea floor spreading.
Explains the origin of connections between earthquakes, volcanoes, faults, continental drift, and sea floor spreading.
Explains how oceans and its features are formed.
Why the ocean floor is not flat?
Oceanic crust is denser than continental crust sinks lower into the mantleThis is why it is filled w/ water and has become an ocean basin.
Typical Features• Continental Shelf-extension of the
continent• Continental Slope- steep drop off
from shelf and end of the continent and it’s crust
• Submarine Canyons- deep valleys in the slope created by underwater landslides or old rivers
• Continental Rise- a pile of sediment that has slid down the slope
• Seamounts and Guyots- Islands created by underwater volcanoes
Features of Ocean Ridges
• Water is superheated (371 C) by hot magma and dissolves minerals from nearby rock
• As water comes out from the rock it looks like smoke
• Area with these hot springs is called a hydrothermal vent
Animals from hydrothermal vents
•Bacteria are the base of the food chain
•Chemosynthesis- make sugars using energy from compounds like H2S
•Other vent animals include giant tubeworms, crabs, octopus, shrimp and mussels