Physical weathering - Geography for You

Physical weathering

Physical weathering
Physical weathering

The Earth’s surface is constantly changing It is a dynamic environment Plate tectonics and volcanism create mountains Chemical decay and physical breakup, combine  with rainfall, ice, snow, wind and gravity to wear away those mountains.

Surface Processes
There are 3 major surface processes that continually breaking rock apart and moving the debris to lower elevations
➽Mass wasting

➤Weathering is the general process by which rocks are broken down on the Earth’s surface
➤Mass wasting is the transfer of rock and soil down slope under the influence of gravity
➤Erosion is the physical removal of rock and soil by water, wind, or ice All three processes can  act at the same time.

Weathered Mountains
The Appalachian Mountains in eastern North America once towered more than 9,000 meters (30,000 feet) high—taller than Mount Everest! Over millions of years, weathering and erosion have worn them down. Today, the highest Appalachian peak reaches just 2,037 meters (6,684 feet) high. (National Geographic)
Three Types of Weathering

> Physical weathering
> Chemical weathering
> Biological weathering

           ➤ Physical weathering
Mechanical weathering is the physical breakup of rocks into smaller and smaller pieces without changes in the rocks’ composition. Mechanical breakup increases surface area and surface to volume ratio. The more surface that is exposed, the greater the opportunity for weathering.

➜Rocks commonly have natural zones of weakness along which they tended to crack

➜Joints are large cracks that form in rocks

➜Joints expose more surface area which speeds up weathering

➜Repeated cycles of freezing and thawing are a major source of mechanical weathering

➜Liquid water expands by 9% in volume when it freezes

➜Water freezing in a confined space exerts a tremendous amount of pressure

➜The cliff is slowly eroded away by repeated cycles of freezing and thawing. This processes is also called frost wedging.

➜Over geologic time, the cliff will be completely destroyed. The rocky debris piles up at the base of the cliff in an accumulation called a talus slope.

➜In a very hot desert environment, the daily cycle of heating and cooling can eventually crack small rocks and pebbles.

➜It is believed that some type of chemical weathering may have weakened the rocks and pebbles making them more susceptive to breakage.

➜When large masses of igneous rocks are exposed, especially granite, concentric slabs begin to break loose in a process called sheeting. When the deeply buried pluton is exposed on the surface, the igneous mass is subject to sheeting weathering.

➜A similar process called exfoliation can occur on a smaller scale with thin slabs breaking off of an exposed rock like a peeling onion.

Previous article
Next article

Articles Ads

Articles Ads 1

Articles Ads 2

Advertisement Ads