Plate tectonics Flashcards
Define Plate Tectonics
a theory explaining the structure of the earth’s crust and many associated phenomena as resulting from the interaction of rigid lithospheric plates which move slowly over the underlying mantle.
What is the Continental Drift Theory
Continental drift theory: Continents once formed a supercontinent (Pangaea) and slowly drifted apart. Supported by fossil, geological, and climate evidence.
Describe the Earth’s crust, its layers and composition of each
Outermost layer of Earth’s lithosphere.
Two types: Continental (30-50 km thick, granite-rich) - Older, less dense, forms landmasses.
Oceanic (5-10 km thick, basalt-rich) - Younger, denser, found under oceans.
Evidence for Continental Drift Theory
Fossil Evidence - Similar plants and animals found on now separate continents
Geological similarities - Matching rock formations and mountain ranges across continents.
Fit of coastlines - Coastal outlines of continents fit together like a puzzle
Explain the movement of plates in terms of heat and convection currents in the Earth’s mantle summarised
Movement of plates: Heat-driven convection currents in Earth’s mantle cause plates to move. The mantle’s hot material rises and cools near the surface, creating circular flows. These currents push and drag tectonic plates, leading to their motion.
Describe the process of subduction
One plate sinks below another at convergent boundaries resulting in the recycling of oceanic crust, formation of trenches and volcanic arcs.
Describe the formation of ocean ridges
Plates move apart at divergent boundaries
resulting in the creation of new oceanic crust, forming mid-ocean ridges and rift valleys.
Why does seafloor spreading occur
Seafloor spreading occurs because of mantle convection. Hot material rises, forming magma. Magma solidifies, creating new oceanic crust. Plates move apart, spreading the seafloor. It is a continuous process that widens ocean basins.
What are the three types of boundaries
Convergent Boundaries
Divergent Boundaries
Transform Boundaries
Describe features of convergent boundaries
Plates move towards each other.
Subduction: One plate sinks beneath another.
Creates deep ocean trenches, volcanic arcs, and mountain ranges.
Recycling of old crust.
Frequent and powerful earthquakes.
Dynamic zones with significant geological processes.
Describe features of divergent boundaries
Plates move away from each other.
Magma rises and solidifies to form new crust.
Creates mid-ocean ridges and rift valleys.
Continuous process widening ocean basins.
Fewer earthquakes compared to convergent boundaries.
Dynamic zones shaping the seafloor and oceanic crust.
Describe features of transform boundaries
Plates slide past each other horizontally.
No new crust is created or destroyed.
High frequency of earthquakes due to friction.
Major fault lines are common features.
Connect divergent and convergent boundaries.
Dynamic zones with lateral movement of tectonic plates.
Hot spot
A hot spot is a geologic phenomenon where an area of the Earth’s mantle experiences an upwelling of abnormally hot and buoyant material.
This hot material creates magma, which rises through the crust and can lead to volcanic activity at the Earth’s surface. e.g Hawaii
Significance of Lines of Hot Spots
Lines of hot spots are tracks of volcanic activity that appear to follow a specific path over time as tectonic plates move over a fixed hot spot in the mantle.
These tracks provide crucial evidence of plate movement and the direction and speed of plate motion.
