ch-1-plate-tectonics

Chapter 1: Plate Tectonics

Overview of Major Plates

• Included Plates:

  • North American Plate

  • Juan de Fuca Plate

  • Pacific Plate

  • Caribbean Plate

  • Cocos Plate

  • Eurasian Plate

  • Arabian Plate

  • Indian Plate

  • Philippine Plate

  • African Plate

  • South American Plate

  • Nazca Plate

  • Scotia Plate

  • Antarctic Plate

  • Indo-Australian Plate

Forces Reshaping the Landscape

• Endogenic Forces: Internal forces causing

  • Molten magma movement creates earthquakes, volcanoes, and fold mountains.

  • New rock formation

• Exogenic Forces: External forces reshaping the landscape

  • Actions of wind, rivers, ice, and weathering

  • Processes: Erosion and weathering of rocks, mountains, and valleys

  • Also termed agents of Denudation

Internal Structure of Earth

• Seismic Records: By the 1970s, detailed seismic data revealed Earth’s structure.

• Dimensions:

  • Total radius: 6,437 km from core center to surface

Structure of the Earth

• Layers:

  • Continental and Oceanic Crust: Thin, outermost layers

    • Rigid lithosphere above molten layers

  • Upper Mantle: Below crust, rigid lithosphere

  • Lower Mantle: 3,700°C, mainly molten

  • Outer Core: 4,000-5,000°C, molten

  • Inner Core: Solid, temperatures of 5,000-6,000°C

Crust Composition

• SIAL (Continental Crust):

  • Thickness: 40-60 km

  • Composition: Less dense, richer in silicon and aluminum (e.g., Granite)

• SIMA (Oceanic Crust):

  • Thickness: 6-12 km

  • Composition: Denser, richer in silicon and magnesium (e.g., Basalt)

Plate Tectonic Theory

• Purpose: Explains workings of tectonic cycle

  • Involves collision, separation, and various landforms

  • Convection Currents: Drive plate movements caused by core heat

Development of Plate Tectonic Theory

• Key Contributors:

  • Wegener (1912): Continental Drift

  • Hess (1962): Sea Floor Spreading

  • Wilson, Morgan, Vine, Matthews (1966): Integration of ideas into Plate Tectonic Theory

Historical Movement of Continents

• Continental Drift Visualization:

  • Provides insights into the former configurations of continents (e.g., Pangaea)

  • Jurassic to Present: Evidence of changing locations over millions of years

Plate Boundaries and Their Types

• Boundary Types: Identified by the nature of interactions

  • Constructive/Divergent: Plates pull apart, leading to rift valleys and mid-ocean ridges

  • Destructive/Convergent: Plates collide, causing subduction, volcanic mountains, and trenches

  • Conservative/Transform: Plates slide past each other creating faults (e.g., San Andreas)

Earthquake and Volcano Mapping

• Mapping: Helped identify plate boundaries through historical earthquake and volcano locations

Convection Currents Mechanism

• Description:

  • Hot magma rises, cools, and sinks in an ongoing cycle

  • Drives tectonic plates' movements and creates new rock formations during separation

  • A full cycle takes about half a billion years

Types of Boundaries and Landforms

• Constructive Boundary:

  • Rift valleys, mid-ocean ridges, and volcanic activity (e.g., Iceland)

• Destructive Boundary Types:

  • Continental-Continental: Collision forms fold mountain ranges (Himalayas, Alps)

  • Oceanic-Continental: Subduction leads to volcanic mountains and trenches

  • Oceanic-Oceanic: Forms island arcs and trenches from subducting oceanic plates

Non-Plate Boundary Activity: Hot Spots

• Definition: Volcanoes formed away from plate boundaries (e.g., Hawaii, Yellowstone)

• Mechanism:

  • Magma rising from stationary hot spots creates volcanic activity as tectonic plates move over them

Summary of Plate Tectonics

• Processes: Driven by convection cells and magma flows

  • Formulate various landforms such as fold mountains, rift valleys, and trenches

  • Result in seismic activities including earthquakes and volcanic eruptions

Exam Preparation

• Revision Questions: Refer to specific pages for revision and official questions.