Weather front

Cold fronts and generally move from west to east, while warm fronts move. Because of the greater density of air in their wake, cold fronts and cold occlusions move faster than warm fronts and warm occlusions. and warm bodies of water can slow the movement of fronts. When a front becomes and the density contrast across the frontal boundary vanishes, the front can degenerate into a line which separates regions of differing wind velocity, known as a shearline. This is most common over the open ocean.

A weather front is a boundary separating two of different and is the principal cause of. In fronts are depicted using various colored lines and symbols, depending on the type of front. The air masses separated by a front usually differ in and Cold fronts may feature narrow bands and may on occasion be preceded by or are usually preceded by and The weather usually clears quickly after a front's passage. Some fronts produce no precipitation and little cloudiness, although there is invariably a wind shift

Pressure release

When erosion removes the overlying rock material, these intrusive rocks are exposed and the pressure on them is released. The outer parts of the rocks then tend to expand. The expansion sets up stresses which cause fractures parallel to the rock surface to form. Over time, sheets of rock break away from the exposed rocks along the fractures. Pressure release is also known as "exfoliation" or "sheeting"; these processes result in and granite domes, an example of which is Dartmoor.

In pressure release, also known as unloading, overlying materials (not necessarily rocks) are removed (by erosion, or other processes), which causes underlying rocks to expand and fracture parallel to the surface. Often the overlying material is heavy, and the underlying rocks experience high pressure under them, for example, a moving Pressure release may also cause to occur.

Chemical weathering

New or secondary minerals develop from the original minerals of the rock. In this the processes of and are most important. The process of mountain block uplift is important in exposing new rock strata to the atmosphere and moisture, enabling important chemical weathering to occur; significant release occurs of Ca++ and other minerals into surface waters.

Chemical weathering changes the composition of rocks, often transforming them when water interacts with minerals to create various chemical reactions. Chemical weathering is a gradual and ongoing process as the mineralogy of the rock adjusts to the near surface environment.

Frost weathering

Frost weathering or cryofracturing is the collective name for several processes where ice is present. This processes include frost shattering, frost-wedging and freeze-thaw weathering. This type of weathering is common in mountain areas where the temperature is around the freezing point of water. Certain frost-susceptible soils expand or upon freezing as a result of water migrating via to gro near the freezing front. This same phenomenon occurs within pore spaces of rocks. The ice accumulations grow larger as they attract liquid water from the surrounding pores. 

The ice crystal growth weakens the rocks which, in time, break up. It is caused by the expansion of when freezes, so putting considerable stress on the walls of containment.

When water that has entered the joints freezes, the ice formed strains the walls of the joints and causes the joints to deepen and widen. When the ice thaws, water can flow further into the rock. Repeated freeze-thaw cycles weaken the rocks which, over time, break up along the joints into angular pieces. The angular rock fragments gather at the foot of the slope to form a slope (or slope). The splitting of rocks along the joints into blocks is called block disintegration. The blocks of rocks that are detached are of various shapes depending on rock structure.

Physical weathering

The primary process in physical weathering is (the process by which clasts and other particles are reduced in size). However, chemical and physical weathering often go hand in hand. For example, cracks exploited by physical weathering will increase the surface area exposed to chemical action. Furthermore, the chemical action at minerals in cracks can aid the disintegration process.

Thermal stress weathering is an important mechanism in where there is a large temperature range, hot in the day and cold at night. The repeated heating and cooling exerts on the outer layers of rocks, which can cause their outer layers to peel off in thin sheets. Although temperature changes are the principal driver, moisture can enhance in rock. and range fires are also known to cause significant weathering of and boulders exposed along the ground surface. Intense, localized heat can rapidly expand a boulder.

Positive and negative feedbacks in glacial periods

This low precipitation allows high-latitude snowfalls to melt during the summer. An ice-free Arctic Oceanand more southerly latitudes, reducing the temperatures over land by increased albedo as noted above. Furthermore, under this hypothesis the lack of oceanic pack ice allows increased exchange of waters between the Arctic and the North Atlantic Oceans, warming the Arctic and cooling the North Atlantic. (Current projected consequences of include a largely ice-free Arctic Ocean within 5–20 years, see Additional fresh water flowing into the North Atlantic during a warming cycle may also reduce the (see Such a reduction (by reducing the effects of the would have a cooling effect on northern Europe, which in turn would lead to increased low-latitude snow retention during the summer absorbs solar radiation during the long summer days, and evaporates more water into the Arctic atmosphere. With higher precipitation, portions of this snow may not melt during the summer and so glacial ice can form at lower altitudes

Ice and snow increase the Earth's i.e. they make it reflect more of the sun's energy and absorb less. Hence, when the air temperature decreases, ice and snow fields grow, and this continues until competition with a negative feedback mechanism forces the system to an equilibrium. Also, the reduction in caused by the ice's expansion increases albedo.

Glacials and interglacials

Glacials are characterized by cooler and drier climates over most of the Earth and large land and sea ice masses extending outward from the poles. glaciers in otherwise unglaciated areas extend to lower elevations due to a lower Sea levels drop due to the removal of large volumes of water above sea level in the icecaps.

 There is evidence that ocean circulation patterns are disrupted by glaciations. Since the Earth has significant continental glaciation in the Arctic and Antarctic, we are currently in a glacial minimum of a glaciation. Such a period between glacial maxima is known as an interglacial.

At a meeting of the (December 17, 2008), scientists detailed evidence in support of the controversial idea that the introduction of large-scale rice agriculture in Asia, coupled with extensive deforestation in Europe began to alter world climate by pumping significant amounts of greenhouse gases into the atmosphere over the last 1,000 years. In turn, a warmer atmosphere heated the oceans making them much less efficient storehouses of carbon dioxide and reinforcing global warming, possibly forestalling the onset of a new glacial age