Bell Ringer How do you think the Sea Floor affects the Ocean?

MARINE BIOLOGY Essential Question: How was the sea floor formed and what is it’s impact on the earth? Learning Goals: Learn the geological structure of the Earth and accepted theory of Earth’s formation. Explore the origin and structures of the ocean basins Agenda: N/A Upcoming: Chapter 3: Chemical and Physical Features of Seawater and the World Ocean

The Sea Floor Chapter 2

Introduction The oceans are not simply places were the land happens to be covered by water. The sea floor is geologically distinct from the continents! The sea floor is locked in a perpetual cycle of birth and destruction that shapes the oceans and controls much of the geological history of the continents. The geological processes that occur at the bottom of the ocean affect the oceans and dry land as well!

The Water Planet Our planet is mostly WATER Land coverage = 39% of the surface! Water coverage = 71% of the surface! The oceans are NOT distributed evenly! Northern Hemisphere = 61% Water Southern Hemisphere = 80% Water

Classification of the Oceans The Oceans are traditionally classified into FOUR large basins! Pacific Ocean : Largest & Deepest! (Contains the Mariana Trench*) Atlantic Ocean : Larger than Indian but equally deep. Indian Ocean : Smaller than Atlantic but equally deep. Arctic Ocean : Smallest & Shallowest! Southern Ocean* (NOT one of the “Big 4” but considered by oceanographers as the body of water continuously surrounding Antarctica) Although they are names separately oceanographers consider them a World Ocean since they are all interconnected. Best seen when viewing the earth from the south pole!*

The 4 Major Oceans + “Southern Ocean”

The Oceans (Southern Pole View)

Structure of the Earth The Earth originated 4.5 Billion years ago. Composed of remnants of the Big Bang (Occurred 13.7 Billion years ago) Earth was formed by continuous aggregation of dust particles into larger and larger particles giving rise to a large rocky planet. Continuous impact and accumulation of rocky substance generated heat through friction leading early earth to have a MOLTEN appearance! “Molten Earth” allowed for materials to settle according to their density. Recall Density = Mass / Volume* Denser materials settled in the INWARD forming the CORE & Lighter materials settled on the SURFACE forming the primitive CRUST. https://www.youtube.com/watch?v=57merteLsBc

Dissection of the Layers of the Earth

Earth’s Anatomical Breakdown Core Inner Core : Solid Outer Core : Liquid Mantle Lower Mantle: Solid Upper Mantle : Mostly Solid Asthenosphere (outermost mantle) is plastic. Crust Lithosphere: Solid (Rock) Crust: Solid (outermost surface) Depth of Crust = 3 to 44 miles The Kola Superdeep Borehole is only 7.6 miles

Continental and Oceanic Crusts The geological distinction between the ocean and continents result from the physical and chemical differences in the rock that makes up the crust. Oceanic Crust (Sea Floor) = Basalt Rock Make up the sea floor Dark colored Oldest are less 200 million y/o Denser than Granite rock Continental Crust = Granite Rock Make up continents Variant color Oldest are 3.8 billion y/o Less Dense than Granite Rock

Basalt Rock

Granite Rock

Origin and Structure of the Ocean Basins People originally viewed the world as static and unchanging. In 1620, Sir Francis Bacon noted the coasts of the continents on opposite sides of the Atlantic fit together like pieces of a puzzle. It was much later noted that coal deposits, fossils, and other geological formations match on opposite sides of the Atlantic. In 1912, Alfred Wegener (Geophysicist) proposed detailed hypothesis of Continental Drift. Proposed the continents were once joined together as a “supercontinent”. He named this supercontinent Pangea.

Pangea

The Theory of Plate Tectonics Wegener’s Hypothesis was NOT widely accepted because he could not explain how the continents moved. Later proposals also failed due to lack of workable mechanism. In the late 1950’s & early 1960’s all available evidence was combined to conclude the continents drifted apart by way of Plate Tectonics. Wegener was RIGHT!

Fossil Proof of Pangea