Earth Science: Geology and Plate Tectonics

• Earth science is a broad term encompassing all scientific fields related to the planet Earth
• Includes the study of Earth's structure, composition, processes, and history
• Sub-disciplines of Earth science: geology, oceanography, atmospheric science, environmental science

Geology

• Focuses on the Earth's physical structure and substance, its history, and the processes that act upon it
• Includes the study of rocks, minerals, landforms, and the forces that shape them
• Key areas of geology: mineralogy, petrology, structural geology, geomorphology, paleontology, stratigraphy, economic geology, engineering geology, environmental geology, hydrogeology, geochemistry, geophysics

Plate Tectonics

• Theory explaining the structure of the Earth's crust and its associated phenomena as resulting from the interaction of rigid lithospheric plates that move slowly over the underlying mantle
• These plates float on the asthenosphere, a more ductile part of the upper mantle

Plate Boundaries

• Divergent boundaries: Plates move apart, resulting in upwelling of magma from the mantle to create new crust
• Mid-ocean ridges are a prime example of divergent boundaries, where new oceanic crust is formed
• Convergent boundaries: Plates collide, resulting in subduction (one plate slides beneath another) or collision (plates crumple and fold)
• Oceanic-continental convergence: The denser oceanic plate subducts beneath the continental plate, leading to the formation of volcanic arcs on the continental plate above
• Oceanic-oceanic convergence: One oceanic plate subducts beneath another oceanic plate, forming volcanic island arcs
• Continental-continental convergence: Both plates are buoyant, resulting in collision and mountain building (e.g., the Himalayas)
• Transform boundaries: Plates slide horizontally past each other, neither creating nor destroying lithosphere
• Earthquakes are common along transform boundaries (e.g., San Andreas Fault)

Driving Forces

• Mantle convection: Heat from the Earth's core drives convection currents in the mantle, which in turn exert forces on the lithospheric plates
• Ridge push: Newly formed crust at mid-ocean ridges is hot and elevated compared to the surrounding seafloor; as it cools and moves away from the ridge, it becomes denser and slides down the slope, pushing the plate ahead of it
• Slab pull: As an oceanic plate subducts into the mantle, it becomes denser than the surrounding mantle; this density contrast creates a force that pulls the plate downward, effectively dragging the rest of the plate along with it