Canyon Pleto

It developed over 40 million years ago. Origins of canyon begins 17 million years ago. It is a calcite deposits. Canyon is a result of erosion, which exposes on of the most complete geological columns on the planet.

Here erosion is caused by

  1. Water
  2. Ice
  3. Air(wind).

Major cause of erosionsand canyon formations are the course of Colorado river itself. Volcanism, Continental drift and slight variation of the earth orbit. Soil in Grand Canyon is baked by the Sun and it tends to becmoe very hard. This hard rock can not absobrbs much water when it rains. When it rains the water tends to come in rush and add to the problem. The plants the grow in Grand Canyon tend to have roots with very little depth, so they do not grab/hold as much water as possible. This root system do nothing to erosion by holding soil. Now this huge amount of water go down to Colorado river, nothing holding the soil and rock in place. The result is frequent flush flood rolling down the side canyon. Erosion by ice is the second largest powerful force of sunch formation of Gand Canyon. Water from ice seeps in crack between the rocks. These cracks are caused by sesmic activities or by constant soaking or drying of rocks. When water freezes, it expands and expanse cracks and eventually pushed off into the side canyons.

Unconformities

Unconformities are stratified rocks and are therefore usually found in sediments. They are the surface between two rock mass, which constitutes substantial breaks. Unconformity represents times when deposition stopped. An interval of erosion removes some of the previously deposited rocks and finally deposition was resumed.

Types of Unconformity

  1. Angular unconformity.
  2. Disconformity
  3. Nonconformity.

Angular Unconformity

When older sedimentary bed has been tilted and brought to an untimely cut short by erosion and the younger bed was deposited by erosion surface.

Process Evolved in Agular Uncorformity : First substance. Over it deposition occurrs. There after the rock is uplifted and then tilted. In course of time, uplifted part was eroded and then subsided again. Sea/huge water body covers this subsided region and again deposition occurs on top of the previous rock. This cycle repeats itself in due course of time.

Grand Canyon is the Grand Example of Grand Geological Angular Unconformity

Tilted sedimentary rock of pre cambrian age, are overlayed by yonger sedimentary rock of phanerozoice age. In Utah a lines of sandstone rocks near sea are the unique example of disconformity of rocks. Chinle formation happen in triasic period.

NonConformity are also unconformities and it separates igneois or mermorphic rock from over lying sedimentary rock.

Non conformity at the base of grand canyon

The dark rock of the bottom are Archian Vishnu Schist and are over lain by protosoic and phenosoic sediment. Wyoming river a narrow valley with steep rocky wall are non conformities.

Unconformity involves three process,

  1. Uplift.
  2. Erosion.
  3. Subsidence. During growth of continet, as earth history progressed. In Grand canyon 40 major layers are exposed.

Bottom most basement rock in Grand Canyon - Visnhnu Basement Schist

Color:purple. This rock is deposited as volcanic rocks and sediments. Later metamorphososed. Vishnu metamorphic rock is early protarosopic crystalline rock, consists of granitic, pigmatite. aplit intruded by paleoprotasoic rock.