Earth Science: Endogenic Processes

Earth Science: Endogenic Processes

• Lesson Objectives:
  • Identify sources of Earth's internal heat.
  • Explain rock behavior under stress.
  • Discuss seafloor spreading.

Earth's Internal Heat Source

• Primordial Heat:

  • Internal heat remaining from the planet's early stages.
  • Energy accumulated by dissipation during the first few million years of evolution.

• Radioactive Decay:

  • Spontaneous breakdown of atomic nuclei.
  • Releases energy and matter from the nucleus.

• Gravitational Pressure:

  • Gravity compresses an object.
  • Reduces size and increases density.

• Dense Core Material:

  • Inner core's intense pressure prevents iron and other elements from melting.
  • Pressure and density are too great for iron atoms to become liquid.

Rock Behaviors Under Stress

• Stress:

  • Force per unit area placed on a rock.

• Types of Stress:

  • Tensional Stress: Rocks are pulled apart, lengthening and breaking. Found at divergent plate boundaries.
  • Compressional Stress: Rocks are squeezed together, folding or fracturing. The most common stress in convergent plate boundaries.
  • Shear Stress: Forces slide past each other in opposite directions resulting in slippage and translation. Common in transform plate boundaries.

Geologic Structures

• Folds:

  • Formed when rocks experience compressive stress and deform plastically.
  • Cause bending of rocks.
  • Types of Folds:
    • Monocline: A simple bend where the oldest rocks are at the bottom and youngest at the top.
    • Anticline: An upward arching fold with the oldest rocks at the center.
    • Syncline: A downward curving fold with the youngest rocks at the center.

• Faults:

  • Cracks or fractures in rocks due to stress.
  • Joints: Fractures where a block of rock is left standing on either side.
  • Footwall: Rock layer above the fault.
  • Hanging Wall: Rock layer below the fault.
  • Fault Scarp: A visible cliff caused by a fault.
  • Types of Faults:
    • Normal Faults: Common at divergent boundaries, hanging wall moves down relative to the footwall.
    • Reverse Faults: Common at convergent boundaries, hanging wall moves up relative to the footwall.
    • Strike-Slip Faults: Common at transform boundaries, rocks move sideways past each other.

Seafloor Spreading

• Process: Occurs at mid-ocean ridges. Creation of new ocean floor through volcanic activity.

• Proposed by: Harry Hess in 1962.

  • Contends that convection in Earth's mantle is the driving force.

Sonar

• A device that bounces sound waves off underwater objects to determine depth.

Evidences Supporting Seafloor Spreading

• Molten Materials: Rocks (pillow rocks) show repeated eruptions from cracks at the mid-ocean ridge.
• Magnetic Strips: Pattern of magnetized stripes on the ocean floor reflect reversals in Earth's magnetic field.
• Drilling Samples: Older rocks are found farther from the mid-ocean ridge, and the youngest rocks are at the ridge.

Structure and Evolution of Ocean Basins

• Continental Shelf: A partially shallow extension of the continent under water.
• Continental Slope: Transition zone from the continental shelf to the deep ocean floor, starts from oceanic crust to continental crust.
• Continental Rise: The place where the oceanic ocean begins, where sediment from land washes.
• Abyssal Plain: The flattest part of the ocean, covers 50% of the Earth's surface.
• Island: Part of the ocean basin that extends above the ocean floor.
• Seamount: An undersea mountain that was flattened by wave erosion.
• Trench: The deepest part of the ocean.
• Mid-Ocean Ridge: Where upwelling of magma creates new seafloor.

Wilson Cycle

• Explains the opening and closing of oceans due to plate tectonics.
• Named after J. Tuzo Wilson.
• Stages:
  • Embryonic Ocean Basin
  • Juvenile Ocean Basin
  • Mature Ocean Basin
  • Declining Ocean Basin
  • Terminal Ocean Basin
  • Suturing

Explore the intriguing endogenic processes that shape our planet in this quiz. Learn about the sources of Earth's internal heat, the behavior of rocks under stress, and the dynamics of seafloor spreading. Test your knowledge of these fundamental concepts of Earth Science.