Earth Science, Tarbuck Chap 4 Flashcards
The Continental Drift Theory was proposed by
Alfred Wegener
Single Supercontinent Composed of all of Earth’s Landmasses
Pangaea
What caused Alfred Wegener to pursuit the possibility of Pangaea existing
identical fossil organism in the rocks on both South America and Africa
What organisms did Wegener use to support his theory
Mesosaurus and Glossopteris
Pangaea was located mostly around
South Pole
How did Wegener use Paleoclimate to support his theory
Sometime 300 million years ago there was an ice age that covered tropical and subtropical regions today. He showed that most of the land masses had to have been around the South pole in order for this to happen, as there were also Tropical Swamps in the Northern Hemisphere(of today) in the same period
Oceanic Crust is mostly composed of
Basalt
The density of Ocean Lithosphere is ____ compared to the Continental Lithosphere
Denser
What is the Lithosphere
Rigid outer part of the Earth, consists of Crust and Upper Mantle
What is the Asthenosphere
Hotter, Weaker region in the mantle beneath the Lithosphere
Rocks in the upper Asthenosphere are mostly
Near melting levels, but mostly solid.
How do rocks in the Upper Asthenosphere respond to stress
the rocks flow
How do Rocks in the Lithosphere respond to stress by
Bending or Breaking
The Lithosphere is ____ from the Asthenosphere
Detached
What are the 7 major lithospheric plates
North American, South American, Pacific, African, Eurasian, Australian-Indian, Antarctic
What percent of Earth’s surface is covered by the 7 major lithospheric plates
94%
Largest Lithospheric plate
Pacific Plate
Most divergent plate boundaries are located on
Mid-Ocean Ridges
Where does sea floor spreading occur
Mid-Ocean Ridges
What is the largest topographical feature on Earth’s Surface
Mid-Ocean ridge system
The crest of a Mid-Ocean ridge is often how many kilometers higher than surrounding basins
2-3 kilometers
Why is the Crest of a Mid-Ocean Ridge higher in elevation compared to surrounding basins
the new ocean crust is less dense than surrounding old ocean crust leading to the new ocean crust to rise
What is the rift valley
Canyon-like structure along the crest of the Mid-Ocean ridge caused by the divergent forces pulling the plates apart
What is Sea-Floor Spreading
The mechanism acting along Mid-Ocean Ridges that create new Ocean Crust
Ocean depth ________ as you move away from the Mid-Ocean Ridge
Increases
What is Continental Rifting
When 2 continental Plates diverge, leading to a continental rift or depression to form. It can also be called a rift valley and if they continue rifting it will form a narrow sea and eventually new ocean basin.
The East African Rift is an example of what
A continental Rift
What happens at Convergent Boundaries that balances the surface area of Earth.
Old, dense portions of the Ocean Lithosphere plunges into the Mantle, where it is melted.
Convergent Boundaries often have a plate subducting under another one, which plate is the one that subducts
Oceanic Plate
Old Oceanic Lithosphere is generally _____ compared to the Asthenosphere
2% more dense
Describe Deep-Ocean Trenches
Long, Linear Depressions produced where Oceanic Lithosphere bends as it descends into the mantle as a subduction zone.
The angle at which an oceanic plate subducts is mostly based on
Age and therefore density of the plate(Younger, and less dense, Oceanic Plates subduct at a shallow angle while Older, and Denser, Oceanic Plates subduct at a steeper angle)
When a Descending slab of Oceanic Lithosphere subducts into the Asthenosphere, what is triggered within the hot slab of Asthenosphere above it?
Melting of the Asthenosphere occurs
Why does the introduction of the Oceanic Lithosphere into the Asthenosphere cause the Asthenosphere rocks to melt?
Water and volatiles inside of the Oceanic Lithosphere is forced out because of heat and pressure. This water causes the surrounding rock to melt at substantially less temperatures than normal, kind of like how salt makes ice melt.
What is the process of the melting of Asthenosphere due to the subduction of Oceanic Lithosphere called
Partial Melting
What happens during partial melting
As the melting occurs, the molten rocks(which are less dense) mix with unmelted rock and rise through the lithosphere, which sometimes causes a volcanic eruption.
If partial melting does not cause a volcanic eruption, what else could occur
The molten rock mixture solidifies at depth and thickens the crust.
What are continental volcanic arcs
Mountain systems produced by volcanic activity from Partial Melting
How are Continental Volcanic Arcs and Island Volcanic Arc(or Island Arcs) different
Continental Volcanic Arcs occur at Continental-Oceanic Subduction Zones and Island Volcanic Arcs occur at Oceanic-Oceanic Subduction Zones
What happens at Continental-Continental Convergent Boundaries
Neither Plate subducts and they ram into each other to form a mountain chain.
Where are Transform faults usually found
Ocean Floor
What are Fracture Zones
large linear scars on the ocean floor that are the result of tectonic plate movement
Transform Faults cause the Mid-Ocean Ridge to take what type of structure due to displacement
Step-like structure
What is a mantle plume
Cylindrical Upwelling of Hot Rock originating deep within the mantle
What is a Hot Spot
Area of Volcanism , high heat flow, and crustal uplifting caused by a mantle plume
What is the Curie Point
the specific temperature at which a ferromagnetic material loses its magnetic properties and becomes paramagnetic(weakly attracted to poles)
As Magnetite erupted from Volcanoes Cool, what happens to the grains of the mineral
They Align themselves in the direction of current magnetic lines of force
Describe Magnetic Reversal
When the Magnetic North Pole becomes the Magnetic South pole and Vice versa
When rocks exhibit the same magnetism as the present magnetic field, they are said to possess
Normal Polarity
rocks exhibiting the opposite magnetism are said to have
Reverse Polarity
What are the main driving force in mantle movements
Slab Pull and Ridge Push
Describe Slab Pull
subduction of cold, dense slabs of oceanic lithosphere
Describe Ridge Push
a force that pushes tectonic plates apart at mid-ocean ridges
Which is Stronger, Slab Pull or Ridge Push
Slab Pull
What is the Whole Mantle Convection model
proposes that the Earth’s entire mantle, from the upper to the lower mantle, is involved in a continuous process of convection, where hot material rises and cooler material sinks, creating a large-scale circulation that drives plate tectonics
What is the Layer Cake Convection Model
two zones of convection—a thin, dynamic layer in the upper mantle and a thick, larger, sluggish one located below
In the Whole Mantle Convection Model, the final destination of the subducting oceanic lithosphere is where
Core-Mantle boundary
In the Layer cake convection model, the final destination of the Subducting Oceanic Lithosphere is where
Depths of no more than 1000 kilometers
