Continental Margins

1
Continental Margins

• Continental shelf shallowest part of the margin
• Continental Slope a steeper part
• Continental Rise gently sloping region at the
  base of the of the continental slope consists of
  sediment that piles up on the sea floor

2
Deep Sea Basins

1. Abyssal plain flat area
2. Seamounts old volcanos and islands
3. Trenches deepest part of the ocean
4. Mid Oceanic Ridge main feature of the ocean
   floor
5. Central Rift Valley great gap at the center
   where plates are pulling apart

3
Structure of Earth

• Earth Originated 4.5 billion years ago by the Big
  Bang
• Earths materials were sorted by density
• Densest is found at the center and the least on
  the outside

4
Structure of Earth

• Internal Structure
• Inner Core composed of Fe Ni, high pressure and
  temperatures reach 5,000oC solid in nature
• Outer Core Same elements and temperature but
  less pressure so is a liquid
• Mantle Contains Si and O, semi-solid state that
  moves like molasses
• Asthenoshere-upper mantle
• Crust outermost layer, extremely thin, rigid
  skin floating on the mantle (Oceanic and
  Continental)
• Lithosphere-uppermost mantle and crust

5
Earths Crust

• Oceanic Crust
• Consist of Basalt
• 200 myo
• Dense and thin

• Continental Crust
• Consist of granite
• 3.8 byo
• Not dense and thick

6
Continental Drift

• Proposed in 1920 by Alfred Wegener
• Theory states that all the continents had once
  been joined in a single super continent called
  Pangaea, 180 mya
• Wegener was laughed at due his inability to
  proposed a mechanism for the movement of
  continents

7
Continental Drift

• Evidence
• Coal deposits
• geological formations
• fossils match up on opposite sides of the
  Atlantic
• Jigsaw puzzle like appearance of continents
• Glacial rock deposits
• Limestone and salt deposits

8
Seafloor Spreading Evidence

• Discovery of the Mid Ocean Ridge
• Discovered using sonar
• Interrupted by large geological fault called
  transform faults
• EX Mid-Atlantic Ridge and East Pacific Rise

9
Seafloor Spreading Evidence

• Magnetic Reversals
• Discovered by the Glomar Challenger in 1968
• Symmetric Pattern of Magnetic Bands in the
  seafloor from reversals of the magnetic poles
• Opposite matching bands on either side of
  mid-oceanic ridge

10
Seafloor Spreading Evidence

• Sediment Age and thickness
• Discovered by the Glomar Challenger
• Thickest and oldest sediments are found farthest
  from the Mid Ocean Ridge

11
Seafloor Spreading

• Proposed by Henry Hess in 1960s
• Theory states that mantle rises up at the Mid
  Ocean Ridges is then cooled, placed on the
  seafloor and moved towards the continents
• Mechanism was thought to be convection of the
  mantle beneath the seafloor

12
Plate Tectonics

• Combination of Continental Drift and Seafloor
  Spreading
• Theory earths surface is covered by a fairly
  rigid layer composed of the crust and the
  uppermost part of the mantle called the
  lithosphere that is broken into plates which move
  over the mantle

13
Plate Collisions

• Oceanic Plate to Oceanic Plate
• Causes trenches, earthquakes, volcanoes and
  island arcs
• EX Aleutian Island in Alaska

14
Plate Collisions

• Oceanic Plate and Continental Plate
• Creates a trench, earthquakes, continental
  volcanoes
• Seafloor is destroyed at the trench which
  explains why the seafloor is so young

15
Plate Collisions

• Continental Plate and Continental Plate
• Create mountains
• EX Himalayan Mountains

16
Plate Movements

• Apart plates do move apart and create new crust
• EX mid ocean ridge and Iceland
• Shear Boundary plate are able to slide past
  each other
• EX Californias San Andreas Fault

17
Marine Sediments

• Hydrogenous
• Result from chemical reactions within seawater
• Cosmogenous
• Result from outer space
• Lithogenous Sediment
• Formed from the weathering and erosion of rocks
• Biogenous Sediment
• Created from the skeleton or shells of marine
  organisms
• Calcareous made of calcium carbonate
• Siliceous made of silica

18
Hot Spots

• Stationary plume of magma under a moving plate
• Creates volcanic islands in the middle of plates
• EX Hawaiian Islands and the Emperor Seamount
  Chain