Plate Tectonics Overview

Study Notes

Plate Tectonics Overview

Plate tectonics is a theory explaining the structure and dynamics of Earth's lithosphere.
The lithosphere is divided into several large and small rigid plates that move relative to each other.
These plates interact at their boundaries, leading to various geological phenomena like earthquakes, volcanoes, and mountain building.

Types of Plate Boundaries

Divergent Boundaries: Plates move apart, creating new crust.
- Magma rises to the surface, forming volcanic activity.
- Mid-ocean ridges are prominent features at divergent boundaries.
- Example: Mid-Atlantic Ridge.
Convergent Boundaries: Plates collide.
- Oceanic-Continental Convergence: Oceanic plate subducts beneath the continental plate, creating volcanic mountain ranges on land (e.g., Andes).
- Oceanic-Oceanic Convergence: One oceanic plate subducts beneath another, forming volcanic island arcs (e.g., Japan).
- Continental-Continental Convergence: Two continental plates collide, creating massive mountain ranges. (e.g., Himalayas).
- Earthquakes are common along these boundaries due to the intense pressure and friction.
Transform Boundaries: Plates slide past each other horizontally.
- These boundaries are characterized by frequent earthquakes.
- Example: San Andreas Fault.

Theory of Continental Drift

Proposed by Alfred Wegener in the early 20th century.
Suggested that continents were once joined in a supercontinent (Pangaea) and have drifted apart over millions of years.
Supported by evidence such as the jigsaw-like fit of continents, similar fossil distribution across continents, and matching geological structures.
Initially rejected due to a lack of a viable mechanism for continental movement.

Seafloor Spreading

A process where new oceanic crust is formed at mid-ocean ridges.
Magma rises from the mantle and solidifies, creating new crust that pushes older crust away from the ridge.
Evidence for seafloor spreading includes magnetic stripes in the seafloor, which record reversals in Earth's magnetic field over time.
This process is driven by convection currents in the Earth's mantle.

Convection Currents

Convection currents are the movement of heat within the Earth's mantle.
Hotter, less dense mantle material rises, while cooler, denser material sinks.
This cyclical movement plays a crucial role in driving plate tectonics.
The heat source for convection currents comes from radioactive decay in the Earth's core.

Interior of Earth

The Earth's interior is divided into layers based on composition and physical properties.
Crust: Outermost layer, relatively thin, and composed of solid rock.
Mantle: Thick layer beneath the crust, composed of semi-molten rock.
Outer Core: Liquid layer of nickel and iron.
Inner Core: Solid sphere of nickel and iron under immense pressure.
The movement of material in the mantle, driven by convection currents, is crucial for the movement of tectonic plates.
The inner core's intense heat is another important component of the Earth's internal heat engine.

Description

Explore the fundamental concepts of plate tectonics, including the structure and dynamics of Earth's lithosphere. Learn about the different types of plate boundaries, such as divergent, convergent, and transform boundaries, and their associated geological phenomena like earthquakes and volcanic activity.