Untitled Flashcards Set
What is continental drift?
Continental drift is the movement of continents (Pangaea) resulting from the motion of tectonic plates.
What is some evidence for Pangaea and Continental Drift?
Trilobite fossils from SW Scotland are also found on the other side of the Atlantic Ocean
Fossil evidence of the freshwater reptile Mesosaurus found in South America and SW Africa
Fossils of Glossopteris are found in ALL of the Southern Continents showing they were once joined
Land Shapes (fit well together)
Plate tectonics directly caused the formation of Pangea, a supercontinent, by slowly pushing different continental plates together over millions of years, eventually merging them into one large landmass; it also later caused Pangea to break apart as the plates continued to move and drift away from each other, forming the continents we see today.
Key points about plate tectonics and Pangea:
Formation:
As tectonic plates collided and converged, they pushed the continental masses together, creating Pangea.Breakup:
The movement of tectonic plates at divergent boundaries caused Pangea to rift and split apart, forming the different continents we see now.
Structure of Earth’s Interior
Come More Often Interior
Crust (0 -50km thick)
Lithosphere (crust and upper most solid mantle)
Lightest Density @ 2.2 g cm^-3
Mantle (2900km)
Asthenosphere
Outer Core (2250km)
Inner Core (1300km)
Densest (12.8 g cm^-3)
How do we know about Earth’s Interior?
We primarily learn about Earth's interior through the study of seismic waves generated by earthquakes, a technique called seismic tomography, which analyzes how these waves travel through different materials at varying speeds depending on their density, allowing scientists to create 3D models of the Earth's internal structure and identify distinct layers like the crust, mantle, and core.
Seismic tomography - earthquakes
Transmission of seismic waves
- cooler areas: higher velocity
- hotter areas: slower velocity
Density: P-waves and S-waves react differently to changes in density
S-waves cannot move through liquids with very low viscosity
What is an S-wave shadow zone?
An S-wave shadow zone exists because S-waves, a type of seismic wave, cannot travel through the Earth's liquid outer core, meaning that seismographs located on the opposite side of the Earth from an earthquake epicenter will not detect any S-waves, creating a "shadow zone" where no S-waves are received; this discovery provided evidence for the existence of a liquid outer core within the Earth.
Key points about the S-wave shadow zone:
S-wave properties:
S-waves are transverse waves, meaning they move perpendicular to the direction of wave propagation, and can only travel through solid materials.
Mantle Convection
Mantle Convection. Mantle convection describes the movement of the mantle as it transfers heat from the white-hot core to the brittle lithosphere. The mantle is heated from below, cooled from above, and its overall temperature decreases over long periods of time. All these elements contribute to mantle convection
A convection cell is a circular pattern of fluid movement where warm fluid rises, cools, and then sinks, creating a continuous loop; while upwelling is a specific oceanographic phenomenon where cold, nutrient-rich deep water rises to the surface, typically driven by wind patterns along coastlines
Volcanoes around the world
Volcanoes around the world match most plate boundaries
Yes, this statement is true; the vast majority of volcanoes on Earth are located along plate boundaries, particularly at convergent plate boundaries where one plate subducts beneath another, creating the most volcanic activity, often referred to as the "Ring of Fire" around the Pacific Oceans.
Earthquakes around the world
Earthquakes around the world are primarily related to plate tectonics, meaning most seismic activity occurs along the boundaries where tectonic plates meet, collide, slide past each other, or pull apart, with the most significant earthquake zones found around the Pacific Ocean's "Ring of Fire" due to intense subduction activity between plates
Two Types of Crusts
Continental Crust
25-100km thick
Less dense
Younger
Bigger crystals
Oceanic Crust
5-10 km thick
More dense
Older
Tiny crystals
Divergent/Constructive Boundaries
A divergent, or constructive, plate boundary is where tectonic plates pull apart, causing new oceanic crust to be created through a process called "seafloor spreading" as magma rises from the Earth's mantle to fill the gap between the separating plates, essentially building new seafloor along the mid-ocean ridges; this is considered a constructive boundary because new crust is being formed.
Rifting Development
Rifting is defined as the splitting apart of a single tectonic plate into two or more tectonic plates separated by divergent plate boundaries. The rifting of a continental tectonic plate creates normal fault valleys, small tilted block mountains, and volcanism.
Magnetic Properties of the Sea Floor
Geomagnetic reversal: when the magnetic north and south are interchanged
Curie point: the temp at which certain magnetic materials lose their magnetic properties
Convergent (destructive) plate boundary
Ocean-continent convergent boundary
Ocean-ocean convergent boundary
Continent-continent convergent boundary
A "ocean-continent convergent boundary" occurs when an oceanic plate collides with a continental plate, causing the denser oceanic plate to subduct beneath the continental plate, typically forming a deep ocean trench and a line of volcanoes on the continental side
A "ocean-ocean convergent boundary" happens when two oceanic plates meet, with the older, denser plate subducting under the younger one, often creating a chain of volcanic islands known as an island arc
A "continent-continent convergent boundary" is where two continental plates collide, resulting in the formation of large mountain ranges due to the crumpling and thickening of the continental crust, with no subduction occurring as both plates are too buoyant to sink beneath each other.
Transform plat boundaries: slide past each other, san andreas fault
Hotspots: areas in the mantle from which heat rises, forming magma that rises through cracks and erupts to form volcanoes
They form over exceptionally hot regions in the mantle
Ex: yellowstone caldera
Hawaiian hotspot