The Sea Floor CH 2 pg 19

Geosphere

Geological processes influenced terrestrial and marine environments Earth is broken into layers.. Crust Mantle Core (inner/outer)

Geological Layers of Earth Crust - 1% Earth’s mass thinnest layer Continental Granite, less dense, floats on top oceanic Oceanic Basalt, dense, thinner than continental

Lithosphere is part of the upper mantle

Mantle - layers beneath the crust Lithosphere (broken into plates; tectonic) Asthenosphere (plates float on top) “Silly putty” Heated and becomes less dense so material rises then as it cools material sinks creating circulating currents called convection currents Causes plates to move

Geological Layers of Earth Core - innermost layer Outer core Dense liquid Moves counter clockwise thought to create magnetic field Inner core Solid due to pressure Iron and Nickel

Oceans 71% of Planet Regulate climate and atmosphere

Geography of the Ocean Basin 2/3 of the earth’s land area in the Northern Hemisphere The Southern Hemisphere 80% of the ocean

Five Large Basins Pacific Ocean Atlantic Ocean Indian Ocean deepest (approx. 14000 ft) and the largest narrowing Atlantic Ocean Slowly getting bigger Indian Ocean Arctic Ocean Southern Ocean Difference between ocean and sea?

The Origin and Structure of the Ocean Basins (1912) Continental Drift Theory All the continents had once been joined in a single “supercontinent” called Pangea Approx 180 m.y.a. (1950s and 1960s) Plate tectonics Plates did drift lead to the discovery of the Mid-Ocean Ridge

Evidence Pieces of a puzzle Matching sequences of rock & mountains Distribution of organisms Magnetic fields Igneous rock Magnetite and iron

The Mid-Ocean Ridge System of volcanic mounts that encircles the globe Largest geological feature on earth Submarine mountains can break the surface of the water to form islands (ex. Iceland) Eastern – Pacific Ridge (Subduction)

Subduction vs Divergent

Creation of the Sea Floor Pieces of oceanic crust separate mid-ocean ridges by creating cracks called rifts. Rifts release the pressure on the mantle Reduced pressure allows hot mantle material to rise up through the rift.

The magma pushes up around the rift It cools as it enters the surrounding water Creating a ridge Atlantic Ocean getting larger (Divergent)

Creating New Seafloor Repeating process makes the seafloor move away from the mid-ocean ridge Mid-ocean ridge form the edges of continents As the plates move the continent is carried with it (2.5 ~ 7cm/year) Seafloor younger closest to the ridge

Aleutian Islands pg 28 Trenches curve due to Earth’s spherical shape Volcanic islands follow trenches Island Arcs

Hot Spots pg 36 Hawaiian Islands (plate movement) vs Aleutian Islands (subduction) Hawaiian Islands are formed as a result of the movement of plate over a “hot spot” Magma oozes from the thinner oceanic crust Cools and creates a seamount Eventually breaks the surface Southern islands are younger

Continental Volcanoes pg23 Collision between ocean and continental plates result in volcanoes Continent vs Continent Himilayas & Great Smokey Mountains

Transform Boundaries Shear boundary Plates that slide past each other Friction prevents the plates from sliding smoothly They lock up and stress builds up until the plates break free Cause an earthquake San Andres Fault (pg 29)

The Ocean Floor Sea floor is dominated by plate tectonics Sea floor is divided into two main regions; Continental margin Deep-sea floor

Continental Margins Region between the continental crust and oceanic crust Continental Shelf Continental Slope Continental Rise

Continental Shelf Shallow makes up 8% of the ocean’s surface area 400-600 ft deep Rich in life ends at the shelf break Continental crust covered in sea water

Continental Slope Exact edge of the continent Starts at the shelf break Descends to the deep-sea

Continental Rise Sediment forms at the base of the continental slope

Deep-Ocean Basins Mariana Trench 10,000 – 16,500 ft deep abyssal plain West Pacific Depth of 36,163ft (7 miles)

Hydrothermal Vents Fractures in crust water seeps down Heated water pushes its way up Creating a hydrothermal vent Temp ranging from (50 – 550o) The water contains minerals and sulfides

As the water cools the minerals solidify and deposit themselves around the vents creating chimneys, commonly called black smokers. Tallest chimney so far rises 200 ft above sea floor