Geological Processes and Mountain Formation 4/15

Significant Geological Events

• Collision of Continents and Mountains Formation
  • Major deformation occurred from Eocene to Miocene Epochs (approximately 50 million years ago to 30 million years ago).
  • African and Arabian plates colliding create the Himalayan Mountains as a result of collision orogeny.
  • The Himalayan Mountains continue to rise due to ongoing collision between the Indian plate and the Asian plate at a rate of 5 cm per year.

Geological Time Scale

• Key Epochs:
  • Paleocene
  • Eocene
  • Oligocene
  • Miocene
  • Pliocene
  • Pleistocene
  • Holocene (or Toloocene)

Characteristics of the Himalayan Mountains

• Formed from the collision of two continents (India and Asia) during the Eocene epoch.
• The collision caused subduction of the ocean floor in front of India, resulting in uplift of the Himalayan region.
• Geologically old ocean floors uplifted to around 40,000 feet, containing limestone and fossils, indicating past underwater environments.
• The mountains are still actively forming due to tectonic processes.

Plate Tectonics and the Ring of Fire

• Ring of Fire
  • A circumferential zone around the Pacific Ocean characterized by high seismic activity due to subduction of the Pacific Plate beneath surrounding plates.
• Causes significant earthquakes (represented by dot sizes in visual aids) and volcanic activity; associated with famous geological features like the San Andreas Fault.

The Laramide Orogeny

• Focused on the formation of the Rocky Mountains; characterized by major uplift and volcanic activity in the western United States during the Cenozoic Era.
• The Farallon Plate subducted under the North American Plate, contributing to the formation of significant geological features.
• Conflicting theories: Current understanding suggests a magma plume may have contributed to the uplift of the Rockies instead of traditional models.

Significance of the Farallon Plate

• The Farallon Plate is now largely a subducted feature, and its remnants can still be observed in the form of the Juan de Fuca Plate which continues to create volcanic activity in the Cascade Range (e.g. Mount St. Helens).
  • Major volcanic eruptions in the Cascades linked to the subduction of the Juan de Fuca Plate.

Important Geological Concepts

• Subduction Zones
  • Common in collisional environments leading to mountain building (e.g. Himalayas) and volcanic activity (e.g. Cascade Range).
• Transform Boundaries
  • Represented by the San Andreas Fault, where plates slide past each other, contrasting with typical subduction patterns.

Current Understanding and Research

• The understanding of mountain formation and geological processes evolves with ongoing research, indicating that traditional interpretations may only capture parts of complex geological histories.
• Importance of ongoing studies to update geological models, revealing deeper insights into the processes that shape our Earth.