Bell Ringer In which ways do tectonic plates move?

MARINE BIOLOGY Essential Question: How do tectonic plates move? Learning Goals: Review concept of Pangea and formation of the Earth. Learn how the tectonic plates move and what structures they form. Agenda: Pangea handout Chapter 2 (part 2) Lecture Upcoming: Chapter 1 Quiz (Due Next Class) Current Event (Due Next Class)

The Water Planet (SLIDE CORRECTION) Our planet is mostly WATER Land coverage = 30% of the surface! Water coverage = 70% of the surface! The oceans are NOT distributed evenly! Northern Hemisphere is 60% Water vs. 40% Land Southern Hemisphere = 80% Water vs. 20% Land

The Sea Floor Chapter 2 (Part 2)

The Mid-Ocean Ridge System Technological advancements developed during World War II led to the first detailed survey of the ocean floor & discovery of the Mid- Ocean Ridge System. The Mid-Ocean Ridge System is largest geological feature on Earth! Appears as a system of submerged mountains that encircle the continents like the seams of a baseball.

Major Features of the Ocean Floor (Cont.) Ridges: Continuous chain of volcanic submarine mountains. Location of the youngest crust Volcanoes are commonly found here. Trenches: Deep depressions where one crust slides under another. Site of older oceanic crust Volcanoes are also commonly seen here Transform Faults: Cracks in the crust that slide passed each other. Earthquakes are common here

Major Features of the Ocean Floor Volcanic Islands: Normally formed by exposed top parts of Ridge Seamount: Submerged mountain Guyot: Flat topped seamount

Magnetic Polarization of the Ocean Crust The Oceanic Crust is composed of sections that change polarity. On average every 700,000 years the earth’s poles are REVERSED! But can occur as often as 100.000 years or 10 Million + years! It takes 5,000 years for the process to be COMPLETED! The measurable change in polarity further proves the crust originates at the ocean ridges.

Sea-Floor Spreading and Plate Tectonics Sea-floor spreading is only part of the story. The Lithosphere (previously discussed) floats atop the asthenosphere (upper mantle) and is divided into Lithospheric Plates! They can contain continents. As the lithospheric plates move, so do the continents on them The boundaries of the lithosphere correspond to the mid-ocean ridges.

Cause of Plate Movement Geologist originally hypothesized plate movement was caused by convection of the mantle onto the lithosphere. The newly accepted hypothesis states older oceanic lithosphere cools and sinks into the mantle, forming trenches. Trench formation pulls on ridge, weakening it, and allows magma to flow through It is still believed magma flow is aided by convection of the upper mantle

Mantle Convection Clip https://www.youtube.com/watch?v=p0dWF_3PYh4

Lithogenous & Biogenous Sediment Lithogenous Sediment Fine Rocks Coarse Rocks Red Clay (Most Common on the ocean floor) Biogenous Sediment: Skeletons & Shells Skeleton and Shells of Marine Organisims Diatoms Radiolarans Foraminiferans Coccolithophorids Microfossils

Geological Provinces of the Ocean The sea floor is divided into main regions Sea Floor Continental Margin Previously discussed The boundaries between continental crust and oceanic ocean.

Continental Margin (Continental Shelf) Most Superficial Submerged Continental Crust Biologically richest part of the ocean Too gradual to see with naked eye 0.6 mi (Pacific Coast of South America) to 470 mi (Artic Coast of Siberia) The Continental Shelf ends at the Shelf Break where it becomes abruptly steeper.

Continental Margin (Continental Slope) Leads from the Shelf to the Rise Considered the edge of the continent Canyons cut across the slope and channel sediments to the sea floor

Continental Margin (Continental Rise) Deepest part of the continental margin Accumulates sediment channeled by the canyons Sediment deposits as a “deep sea fan”. Leads onto the abysmal plane

Active vs. Passive Margins Active Margins Site of Trenches or Ridges Volcanoes and Earthquakes occur here Ex. West Coast of the South America and the Nazca Plate (Trench Created) Passive Margins Margins without Trenches or Ridges Benign areas Ex. Eastern Coast of South America resting on the South American Plate.

MARINE BIOLOGY Essential Question: How do tectonic plates move? Learning Goals: Review concept of Pangea and formation of the Earth. Learn how the tectonic plates move and what structures they form. Agenda: Pangea handout Chapter 2 (part 2) Lecture Upcoming: Chapter 1 Quiz (Due Next Class) Current Event (Due Next Class)