Aspect (geography)

In physical geography and physical geology, aspect (also known as exposure)^[1] is the compass direction or azimuth that a terrain surface faces.^[2]

For example, a slope landform on the eastern edge of the Rockies toward the Great Plains is described as having an easterly aspect. A slope which falls down to a deep valley on its western side and a shallower one on its eastern side has a westerly aspect or is a west-facing slope. The direction a slope faces can affect the physical and biotic features of the slope, known as a slope effect.

The term aspect can also be used to describe a related distinct concept: the horizontal alignment of a coastline. Here, the aspect is the direction which the coastline is facing towards the sea. For example, a coastline with sea to the northeast (as in most of Queensland) has a northeasterly aspect.

Aspect is complemented by grade to characterize the surface gradient.

Soil aspects[edit]

In some locales there are patterns of soil differences related to differences in aspect. Strong slopes with equatorward aspects tend to have soil organic matter levels and seasonal influences similar to level slopes at lower elevation whereas poleward aspects have soil development similarities to level soils at higher elevations. Soils with a prevailing windward aspect will typically be shallower, and often with more developed subsoil characteristics, than adjacent soils on the leeward where decelerating winds tend to deposit more air-borne particulate material. Outside of the tropics, soils with an aspect directed toward an early afternoon solar position will typically have the lowest soil moisture content and lowest soil organic matter content relative to other available aspects in a locale. Aspect similarly influence seasonal soil biological processes that are temperature dependent. Particulate laden winds often blow from a prevailing direction near solar early afternoon; the effects combine in a pattern common to both hemispheres.

The dryness of the , due to the rain-bearing winds moving parallel to the coast.

Dahomey Gap

The summer dryness of the due to the southerly monsoon flowing parallel to the coast. Its wetness during the northeast monsoon is similarly explained.

Coromandel Coast

The anomalous late autumn rainy seasons of central and the coastal zone of northeastern Brazil for the same reason as above.

Vietnam

The unusual dryness of compared to the rest of New Guinea is because the National Capital District lies parallel to the trade winds which have a drying effect. In Gulf Province and Lae, which receives their full force, rainfall during southern winter is exceedingly heavy, with rainfall and thunder storms during the rainy season.

Port Moresby

The relative dryness of the Queensland coast has the same cause as with Port Moresby.

These are usually of importance only in the tropics, but there they produce many unexpected climatic effects: