Orogeny

RECAP

What is the theory that explains and unifies different geologic phenomena?

What is the theory that states that continents were once joined and then they broke apart?

Give 3 evidences of Continental Drift provided by Wegener.

What do you call the remanent magnetism from ancient rocks recording the direction and strength of the Earth’s magnetic field at that time?

What is the theory that states that the seafloor separates at oceanic ridges?

Results of Tectonic Plate Convergence

Colliding plates provide the compressional forces that fold, fault, and metamorphose the thick layers of sediments deposited at the edges of landmasses

Ocean-ocean convergence mainly produces volcanic mountains

These features tend to be long-lived

Examples: Aleutian Islands (Alaska) and Japan

The Japanese Islands

The convergence of the continental block and the subduction of the oceanic plate leads to deformation and metamorphism of the continental margin

Partial melting of mantle rock above the subducting plate generates magma that migrates upward

The types of mountains formed by ocean-continental convergence are volcanic mountains and folded mountains

Examples: Andes (South America) and Cascades

Ocean-Continental Convergence

Ocean-Continental Convergence

Ocean-Continental Convergence

Andes Mountains

Continental crust floats too much to be subducted

At a convergent boundary between two plates carrying continental crust, a collision between the continental fragments will result and form folded mountains

Examples: Himalayas (Asia), Urals (Russia), and Appalachians

Continent-Continent Convergence

Continent-Continent Convergence

Classic folded terrain: well-developed anticline

ZAGROS MTSPERSIAN GULF

AlternatingAnticlines andSynclines

Most mountains are formed at convergent boundaries, but some are formed at divergent boundaries

The mountains that form along ocean ridges at divergent plate boundaries are fault-block (folded) type mountains

Example: the 65,000 kilometer long mid-ocean ridge system

Mid-Atlantic Ridge

Where is the longest mountain range?