Earth Science - Plate Tectonics

Earth Science - Plate TePlate tectonics is a scientific theory that explains

• Plate tectonics theory states that the lithosphere behaves as a rigid layer divided into plates.
• Continental drift theory proposes that continents were originally connected and have drifted apart.
• Seafloor spreading is the process where new oceanic crust forms at mid-ocean ridges.
• Plate Tectonics Theory - Evidence
• Hotspots: Areas of volcanic activity that originate from deep within the mantle. The Hawaiian Islands are an example, with islands showing age progression.
• Paleomagnetism: Study of magnetism in rocks. Changes in rock magnetism show evidence of plate movement and demonstrate an apparent polar wander path relative to the continent.
• Apparent Polar Wandering: The apparent movement of Earth's magnetic poles over time relative to the continents.
• Convection Currents and Forces
• Layer Cake Model: The mantle is divided into two zones of convection, oceanic lithosphere at the trench, ridge push, volcanic trail, with a ridge.
• Whole Mantle Model: Denser oceanic lithosphere sinks at subduction zones, causing descending oceanic plates, rising plumes, and hotspots.
• Ridge Push: Warmer, less dense material rises at mid-ocean ridges and causes a force that pushes plates apart.
• Slab Pull: Denser, colder oceanic lithosphere sinks at subduction zones, pulling the rest of the plate with it.
• Continental Drift Theory - Evidence
• Continental Fit: The shapes of continents, particularly South America and Africa, seem to fit together.
• Fossil Evidence: Similar fossils of plants and animals are found on continents now separated by vast oceans, suggesting a connection in the past.
• Rock and Mountain Similarities: Similar rock structures and mountain ranges are found on continents that are now separated.
• Glacial Evidence: Glacial deposits and striations suggest that glaciers once covered land areas now in different locations.
• Types of Stress
• Tension: Plates move away from each other, causing stretches in rock. Examples include continental rifts and mid-ocean ridges.
• Compression: Plates move towards each other, causing rocks to fold or break. Examples include ocean trenches and mountain ranges.
• Shear: Plates slide past each other, causing rocks to break or change shape. Examples include faults and fault zones.
• Types of Deformation
• Elastic: Rock returns to its original shape after stress is removed.
• Ductile: Rock reshapes without breaking.
• Brittle: Rock fractures or breaks.
• Faults
• Faults are fractures in rocks where displacement occurs.
• Normal Fault: Hanging wall moves down relative to the footwall.
• Reverse Fault: Hanging wall moves up relative to the footwall.
• Strike-Slip Fault: Rocks slide past each other horizontally.
• Oblique Fault: Displacement involves both horizontal and vertical movement.

Test your knowledge on plate tectonics, including theories like continental drift and seafloor spreading. Explore the evidence backing these theories, such as hotspots and paleomagnetism, and understand the role of convection currents in the Earth's mantle.