Areas of Interest Plate Tectonics Plate Boundaries Causes of Plate Tectonics Evidences Earth Tectonic Plates
Plate tectonics (from Greek tektōn "builder") is a theory of geology that has been developed to explain the observed evidence for large scale motions of the Earth 's lithosphere
The outermost part of the Earth's interior is made up of two layers: above is the lithosphere , comprising the crust and the rigid uppermost part of the mantle . Below the lithosphere lies the asthenosphere
The lithosphere is broken up into what are called tectonic plates
The lateral movement of the plates is typically at speeds of 0.66 to 8.50 centimeters per year
This movement is caused by convection current in the mantle
Mid-Atlantic Ridge moves as fast as fingernails grow
These plates move in relation to one another at one of three types of plate boundaries: convergent or collision boundaries, divergent or spreading boundaries, and transform boundaries. Earthquakes , volcanic activity , mountain -building, and oceanic trench formation occur along plate boundaries
Types of plate boundaries
Three types of plate boundaries exist, characterized by the way the plates move relative to each other. They are associated with different types of surface phenomena. The different types of plate boundaries are:
Transform Plate Boundaries
Divergent Plate Boundaries
Convergent Plate Boundaries
The Earth’s Plates
Plate Boundaries and Earthquakes
Transverse bounaries occur where the plates slide laterally past one another The San Andreas Fault in California is one example. Other examples of transform faults include the Alpine Fault in New Zealand and the North Anatolian Fault in Turkey .Volcanoes are rare but earthquakes are common. 1. Transform boundaries
San Andreas Fault, CA
2. Divergent Boundaries
Boundary between two plates that are moving apart or rifting
RIFTING causes SEAFLOOR SPREADING
Features of Divergent Boundaries
Bridge across the Álfagjá rift on the Reykjanes peninsula in southwest Iceland , the boundary of the Eurasian and North American continental tectonic plates.
3. Convergent Boundaries
Boundaries between two plates that are colliding
There are 3 types…
Ocean plate colliding with a less dense continental plate
Subduction Zone: where the less dense plate slides under the more dense plate
VOLCANOES occur at subduction zones
Ocean plate colliding with another ocean plate
The less dense plate slides under the more dense plate creating a subduction zone called a TRENCH
A continental plate colliding with another continental plate
Have Collision Zones:
a place where folded and thrust faulted mountains form.
Hot magma in the Earth moves toward the surface, cools, then sinks again.
Creates convection currents beneath the plates that cause the plates to move.
What Drives the plates?
The Plate Tectonics Model
The Plate Tectonics Model
Evidence for Continental Drift
Puzzle-like fit of the continents
A. Puzzle-like fit of the Continents
The edges of some continents look as if they would fit together like a puzzle.
South America Africa Coast Line Fit:
Fit of Continents Across the Atlantic
B. Fossil Clues: Mesosaurus
A freshwater swimming reptile
Fossils found in South America and Africa.
Wegener thought that this reptile lived on both continents when the continents were connected.
Fossil Clues: Glossopteris
Found in Africa, Australia, India, South America and Antarctica.
Wegener believed that all these areas were connected.
Ancient Fossils: Plants and Dinosaurs
Climate Clues: Glacial Deposits
Glacial deposits and grooved bedrock found in southern areas of South America, Africa, India, and Australia.
Indicates that these continents were once covered with glaciers.
Wegener believed that these continents were covered with ice near Earth’s South Pole at one time.
C. Climatic Clue :Ancient Glaciations
Similar rock structures are found on different continents.
Mountains found in the eastern U.S. are similar to those found in Greenland and western Europe.
The clues found in rocks, support the idea that continents were connected when these rock structures formed.