The Sea Floor Structure of The Earth and The Mid Ocean Ridge Ch. 2 Part 1

Objectives 1.The basic structure of the earth 2.Name the ocean basins 3.Significance of the Mid Ocean Ridge

Bang! The big bang mya all matter and energy of space was condensed into one point about the size of the head of a pin Then, for reasons unknown, it exploded Dust collided and formed pebbles--> rocks--> larger rocks --> etc. Universe is still moving away from the center

Structure of Earth Eventually planets were formed Materials settled according to density d=m/v Core: Innermost layer, dense, hot (7200ºF) Liquid and solid Mantle: Semiplastic, hot Crust: Outermost layer, thin Oceanic and Continental

Continental vs. Oceanic Crust Why does oceanic sea crust lie below sea level and continents are high and dry? Oceanic crust is denser than continental crust!

Measurement Activity/Lab

The Ocean Basins How many are there? Write them down and check with your neighbor.

Some interesting ocean facts Surface area? –140 million square miles (71% of earth’s surface) Average depth of all the oceans? –12,200 ft or 3,720 m Deepest point? –We’ll get there in a minute Highest mountain in the world? –Mauna Kea, HI (big island): 33,474 ft from base on ocean floor –13,680 ft above sea level

Deepest and Biggest? How did these ocean basins form?

Early Evidence 1620 suggested that landmass fit together like a puzzle Rocks, fossils matched up 1912 continental drift was proposed by Alfred Wegner Pangea!

Wagner couldn’t explain how the continents moved Pangea breakup

Discovery of Mid-Ocean Ridge: The World’s Longest Mountain Range (Over 35,000 miles long)

Mid-ocean ridge: –Continuous chain of submarine volcanic mountains Largest geological feature on earth Know where the Mid-Atlantic ridge (follows shape of continents), the inverted “Y (Indian Ocean),” and the East Pacific Rise are all located.

Trenches Trenches: –Deep depressions in sea floor –Most common in the pacific

Deepest part of ocean floor? Mariana Trench (MT). How deep? 36,201 feet deep! Pressure at this depth? –8 tons per square inch! 1,580 miles long and 43 miles wide If Mount Everest, which is the tallest point on earth at 8,850 meters (29,035 feet), were set in the Mariana Trench, there would still be 2,183 meters (7,166 feet) of water left above it!

Discovery of MT 1951, British survey ship, Challenger II –Gave its name for MT’s deepest point, “Challenger Deep.” More on exploration/discovery

Challenger Deep More on Challenger Deep

Puerto Rico Trench Deepest spot in the Atlantic. How deep? 8,400 m (5.2 miles) Part of the North American plate is descending under the Carrebean plate (Puerto Rico and Virgin Islands)

What do you notice about these two maps? Check with a neighbor and discuss.

The Mid-Ocean Ridge: Who Cares? Geological Activity: –Earthquakes --> Ridges –Volcanoes --> Trenches Red dots are volcanoes and earthquakes –Outline of plates

Mid-Ocean Ridge: Who Cares? Age of sea floor Rock at the ridge --> young, little sediment Further away from ridge --> older the rock --> thicker sediment

Mid-Ocean Ridge: Who Cares? Magnetism Earth’s magnetic field periodically reverses –About every 700,000 years (about 170 times in the last 80 million years –Thought to be related to movement in outer core –Compass needle points south instead of north So what?

Mid-Ocean Ridge: Who Cares? Rocks contain magnetic particles When molten --> act as tiny compasses and point north or south Rocks cool --> particles frozen in place Form bands of rock that alternate magnetism Animation What does this mean?

Mid-Ocean Ridge: Who Cares? The sea floor was NOT formed all at once This is a HUGE piece of evidence for sea floor spreading and plate tectonics Sea floor formed in symmetric stripes that parallel the ridge How does this happen?