8.1
Earthquake- Vibration of earth release of energy.
Focus- point within Earth where the Earthquake starts.
Epicentre- Location on the surface directly above the focus
Faults- Fractures in Earth
Seismograph- Instrument used to record Earthquakes
Seismogram- Traces of recorded ground motion.
Notes 2
9.1 Continental Drift
An Idea before its time
Wegner’s continental drift hypothesis stated the continents had once been joined to form a single super continent.
Wegner proposed that the super continent Pangea, began to break apart 200 million years ago, and formed the present landmasses
Evidence
The Continental Puzzle
Matching fossils
Fossil evidence for continental drift includes several fossil organisms found on different landmasses.
Rock types and structures.
-Rock evidence for continental drift exists in the form of several mountain belts that end at the coastline only to re-appear on a landmass across the ocean.
Ancient Climates
Rejected the hypothesis
A new theory emerges
Wegener could not provide an explanation of exactly what made the continental move. Newer technology leads to findings which lead to a new theory called plate tectonics.
Earths major roles
According to the theory of plate tectonics’ the uppermost mantle, along with two overlying crust heaving as a strong ridged layer. This layer is known as the lithosphere.
A plate is one of the numerous rigid sections of the lithosphere that move as a unit over the material of the asthenosphere.
Notes #3
Type of plate boundaries
Divergent boundaries also called spreading centres are the place where two plates move apart.
Convergent boundaries form where two plates move together
Transform fault boundaries are margins where two plates grind past each other without the production or destruction of the lithosphere.
Divergent boundaries
Ocean ridges and seafloor spreading
Ocean ridges are continuous elevated zones on the floor of all major ocean basins. The rifts at the crest of ridges represent divergent plate boundaries.
Rift valleys are deep faulted structures found along the axes of divergent plate boundaries they can develop on the sea floor or land.
Seafloor spreading produces new oceanic lithosphere.
Notes #4
Actions At plate boundaries
Divergent Boundaries
Continental Rifts
When spreading centres develop within a continent, the landmass may split into two or more smaller segments, forming a rift.
Convergent Boundaries
Oceanic-Oceanic
Two oceanic slabs converge and one descends beneath the other this kind of boundary often forms volcanoes that emerge from the sea. Ex. Aleutian, Mariana, Tongan Islands
Continental
When subducting plates contain continental material, two continents collide.
This kind of boundary can produce new mountain ranges, such as the Himalayas.
Convergent Boundaries
A subduction zone occurs when one oceanic plate is forced down into the mantle beneath a second plate.
Oceanic Continental
Dense oceanic slab sinks into the athenosphere packets of magma develop and rise continental volcanic arcs form in part by volcanic activity caused by the subduction of oceanic lithosphere beneath a continent Ex. Andes, Cascaeds, Sierra.
Transform fault Boundaries
At a transform fault boundary, plates grind past each other witout destroying the lithosphere
Transform fault
Most join two segments of a mid ocean range
At the time of formation, thy roughly parallel the direction of plate movement
Paleomagnetism is the natural remnant magnetism in rock bodies, this permanent magnetization acquired by can be used to determine the location of the magnetic poles at the time the rock becomes magnetized.
Normal polarity when rocks show the same magnetism ats the present magnetization field.
Reverse Polarity when rocks sow the opposition magnetism as the present.
Notes #
Evidence for plate tectonics
Hotspots
A hotspot is aconcentration of heat in the mantle capable of producing magma which rises to Earth’s surface; the pacific plate moves over a hotspot, example HI islands.
H.S evidence supports that the plate move over the earths surface.
Causes of Plate movement
Scientists generally agree that convection