Earth Structure and Characteristics
Earth Materials and The Cycle Of Rock Change
Sediments and Sedimentary Rocks
The Cycle Of Rock Change
Relief Features Of The Ocean Basins
Ocean basins include a midoceaning ridge with a central axial rift where crust is being pulled apart
The margins of the Pacific Ocean Basin have deep offshore oceanic trenches
In the North Atlantic Ocean, two large tectonic plates are spreading apart and moving away from a central rift.
Ocean basins are contained in The crust.
opic
Earth continents and ocean basins were created by the continuous movements of Lithospheric plates in geologic timescales on the surface of the Earth
Arc-Continent Collision
Configuration Of The Continent
Earth surface features formed are driven by the lithospheric plates’ movement that slides over the hot viscous asthenosphere.
Configuration of our continents must have changed many times over the history of the earth
Arc-Continent Collison
Continuation of collision leads to formation of new subduction boundary
Another oceanic fracture develops.
Resulting mass of rocks is called an orogen
Formed through the process of orogeny
Layers of sediment on continental shelf and slope are affected
Thrust far inland over older continental rocks
Crushed and deformed
Island arc collides with passive continental margin
Not subducted, but pushed up against the continent
Island arc is thick and buoyant
Continent-Continent Collison
Ancient sutures marking early collision
Caledonian Mountains (Scotland, Norway, Svalbord, Eastern Greenland)
Appalachian Mountains (Eastern North America)
Ural Mountains (Europe-Asia)
Collision zone is called a continental suture
The collision unites two plates
Resulted by the ongoing closing of ocean basin
The Wilson Cycle and Supercontinents
Supercontinent Cycle
Dispersal
Supercontinent Formation
Convergence
The Wilson Cycle
Stage 6 —The Form Of Continental Suture
Stage 5 — Closing Continents
Stage 4B — The Rising Of Island Arcs
Stage 4A — The Closing Of The Ocean Basin
Stage 3 — Old Ocean Basin
Stage 2 — Young Ocean Basin
Stage 1 — Embryonic Ocean Basin
Island Arcs and Collision of Oceanic Lithospheric Plates
Example: Aleutian Islands
Accretionary wedge of sediments forms from piled-up seafloor sediment in the trench
Fracture produces a subduction boundary
Island arc is formed by new volcanoes that grow and fortify from below
Subducted oceanic lithosphere plunges downward, and oceanic crust is carried into the mantle
Melted altered crust forms magma that rises and erupts on the seafloor
Subducted oceanic crust is altered due to water reaction
Subduction occurs when fracture happens at a passive continental margin
Continent ruptures to form an ocean basin with axial rift
Plate motions may reverse and the ocean basin may start to close
Two plates move apart and create a new ocean
Igneous Rocks
Metamorphic Rocks
Types of Metamorphic Rocks
Not Foilated: they have formed in an environment without directed pressure or relatively near the surface with very little pressure.
Foliated: they have formed in an environment with either directed pressure or shear stress.
Definition of Metamorphosis
Metamorphism is a process that changes preexisting rocks into new forms because of increases in temperature, pressure, and chemically active fluids.
Formation
Subtopic
Relief Features Of The Continents
Plate Tectonics
Continental Rupture and New Ocean Basins
Formation process: Initial formation of a rift valley leads to the sinking of the bottom below sea level and allows seawater to enter
Example: Red Sea - triple junction of three spreading boundaries established by the motion of the Arabian plate pulling away from the African plate
Passive continental margins: Where continental lithosphere is joined to oceanic lithosphere with no motion between them
Result: Formation of a wide ocean with an axial rift and passive continental margins on either side
Causes: Tectonic forces uplift a plate of continental lithosphere and pull it apart
Definition: Continental lithosphere fractures and splits apart
The Power Source for Plate Movements
Radiogenic heating
The Descending Theory
Gravity Gliding Theory
Convection Currents Theory
Continental Rupture and New Ocean Basins
The Crust and Lithosphere
Lithospheric plates
can separate or collide to create relief features like continents and ocean basins
large pieces of lithospheric shell that can move independently
Lithosphere
ranges in thickness from 60 to 150 km
including crust and cooler upper part of mantle
brittle rock
outer Earth shell of rigid
Continental crust
consists of lower zone of dense mafic rock and upper zone of lighter felsic rock
Oceanic crust
consists almost entirely of mafic rocks
Contains continents and ocean basins
7-40 km thick
Composed of varied rocks and minerals
Separated from mantle by Moho discontinuity
Thin, outermost layer of Earth
The Mantle
Upper Mantle
molten material forms in hotspots
softer and plastic (asthenosphere)
lower temperature and pressure
Lower Mantle
hotter but largely rigid due to intense pressure
Subdivided into zones with different temperatures and compositions
Largest layer, makes up over 80% of Earth's volume
Temperatures range from 1800°C to 2800°C
Mafic silicate minerals
The Core
Inner Core
extreme pressure keeps it solid despite high temperatures
solid iron
Outer Core
generates a magnetic field
liquid iron
