Mountain Building
Tectonic plates of the world
ISOSTACY
Isostatic Rebound crust rises as a result of removal of mass This iceberg also demonstrates the process of isostatic rebound.
Types of Mountains Folded Mountains (can cause plateaus to form) Volcanic Mountains Faulted Mountains (Fault-block Mountains) Divergent-Boundary Mountains (Mid-Ocean Ridges) Uplifted Mountains (Dome Mountains)
OROGENY All of the collective processes that form a mountain range or mountain belt. EXAMPLE: the Laramide Orogeny formed what are collectively known as the Rocky Mountains. EXAMPLE: Alleghanian Orogeny formed the Appalachian Mountains.
List all of the processes that might contribute to an orogeny.
Principles of Geology UNIFORMITARIANISM James Hutton (1726-1797) The geologic past can be interpreted and explained by referring to present day processes, given enough time. The present is the key to the past Then Charles Lyell (1797-1875) popularized the ideas and is often credited with this principle.
Principles of Geology PRINCIPLE OF SUPERPOSITION Rocks are hardened layers of sediment once laid down under water (Sedimentary rocks only). Layers of rock were laid down sequentially, oldest at the bottom. In an undisturbed sequence of layered rock, the oldest layer is at the bottom and the youngest at the top.
Principles of Geology PRINCIPLE OF ORIGINAL HORIZONTALITY Sedimentary rock layers form from sediment laid down under water. Sediment is laid down under water essentially horizontally. Rock layers were originally lithified horizontally. Any tilting or folding of rock layers indicates they have been moved from their original horizontal position.
Original Position and orientation (horizontal) Deformed by compression Weathering and erosion at the surface Submergence and deposition of new sediment (horizontal)
Principles of Geology Principle of Original Lateral Continuity sediment extends laterally in all directions until it thins and pinches out or terminates against the edges of the depositional basin
Nicolaus Steno (1638-1686) www.gly.uga.edu/railsback/1121steno.jpg
Timeline: order the following events. India collides with the Eurasian Plate. A volcanic arc forms along the edge of the Eurasian continent. Sub-continent of India moves toward Eurasia. Heavy sediments on ocean floor close up the Tethys Sea. Tibet begins to rise. Heavy sediment from ocean floor is pushed upward to form mountain peaks. Folding of rock layers occurs. Weathering and erosion carve and shape the jagged peaks. Volcanic activity along the edge of Asia stops. Uplift of mountains continues.
1. Sub-continent of India moves toward Eurasia. 2. A volcanic arc forms along the edge of the Eurasian continent. 3. Heavy sediments on ocean floor close up the Tethys Sea. 4. Heavy sediment from ocean floor is pushed upward to form mountain peaks. 5. India collides with Asia. 6. Folding of rock layers occurs. 7. Tibet begins to rise. 8. Volcanic activity along the edge of Asia stops. 9. Weathering and erosion carve and shape the jagged peaks. 10. Uplift of mountains continues.
How do we know?
And here are the Appalachians
Folded Mountains Plates collide Folded Mountains occur in the same manner as crumpling a sheet of paper The Himalayas and the Appalachians.
Blue Ridge of the Appalachian Mountains Folded Mountains
The formation of Pangaea formed the Appalachians and the Caledonians.
Faulted Mountains Plates interact and blocks of crust are either thrust upon themselves or are normally faulted. As movement continues, mountains build. Erosion (water, wind, ice) shapes the mountain peaks.
Faulted Mountains The grand Tetons
b
Thrust Faulted Mountains
Basin and Range Mountains (normally faulted)
Volcanic Mountains Subduction: converging plates. One plate is forced under the other Hot magma rises and forms a volcano along the subduction zone Where do we see examples of this today?
Mount Shasta Volcanic Mountain in Northern California Common occurrence in the Ring of Fire
Section 20.1 Crust-Mantle Relationships Seamounts Individual volcanic mountains produced by hot spots under the ocean floor are called seamounts. As a result of isostasy, the oceanic crust around these peaks displaces the underlying mantle until equilibrium is achieved.
Stationary
Uplifted Mountains (sometimes called Upwarped mountains or Dome mountains Caused by forces within the Earth pushing directly up on a part of the crust A bubble of magma rises and cools, pushing overlying rock upward, creating a dome. The Black Hills of South Dakota