How does unloading contribute to weathering

In either case the weathering is more pronounced with more moisture content. Begin typing your search term above and press enter to search. Press ESC to cancel. Skip to content Home Social studies How does pressure release weathering occur? Social studies. Ben Davis January 7, How does pressure release weathering occur?

What weathering is pressure release? How does pressure affect mechanical weathering? This page describes mechanical physical weathering and more. Rocks are naturally fractured at several levels. Mineral grains have boundaries, which can be areas of weakness in the rock.

Sedimentary rocks next time often are layered and the layers sometimes are not bound together well. More massive rocks can have joints cracks which have no relative motion across them, only spreading which will open as the rocks are exposed due to erosion.

Physical weathering acts to widen these rock fractures. This is mostly found in deserts; the actual mechanisms by which it happens are still under study Brandon Vogt did his thesis on insolation weathering of sandstone!

Forest fires and even lightening! Unloading Plutonic igneous rocks form at depth in the crust with an immense volume of rock overburden above them. When these rocks are exposed, and the immense weight of the overburden rock above them is removed, they expand, and zones of weakness open up as joints. Granite tends to open and peel away sheets of rock think of peeling an onion ; the domes in Yosemite are formed by this process, which is called unloading.

There are examples of this type of weathering in the Landslide module as well as the throughout the Weathering module. Over time, successive cycles of freezing and thawing can cause this fracture to expand.

Eventually, a piece of the rock may be broken off along this fracture. An illustration of how ice or frost may act on existing fractures to break rock apart.

Similarly, root wedging is the process by which a plants root system grows into existing fractures and expands these fractures as the roots grow. Thermal expansion describes the effects of heating and cooling on a rock. Over the course of a day, week, year, etc. Consider a rock outcrop in a moderate climate. During the day, this rock is exposed to sunlight, gradually heating the rock and causing it to expand.

As the temperature drops overnight, the rock begins to cool and contract. Moreover, the rock may not be uniformly heated or cooled depending on its orientation and a variety of other factors.