Weathering in the context of "Ancient ruins"

Sediment is a solid material made of loose particles that is transported to a new location where it is deposited. It occurs naturally and, through the processes of weathering and erosion, is broken down and subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand and silt can be carried in suspension in river water and on reaching the sea bed deposited by sedimentation; if buried, they may eventually become sandstone and siltstone (sedimentary rocks) through lithification.

Sediments are most often transported by water (fluvial processes), but also wind (aeolian processes) and glaciers. Beach sands and river channel deposits are examples of fluvial transport and deposition, though sediment also often settles out of slow-moving or standing water in lakes and oceans. Desert sand dunes and loess are examples of aeolian transport and deposition. Glacial moraine deposits and till are ice-transported sediments.

In geology, a rock (or stone) is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its chemical composition, and the way in which it is formed. Rocks form the Earth's outer solid layer, the crust, and most of its interior, except for the liquid outer core and pockets of magma in the asthenosphere. The study of rocks involves multiple subdisciplines of geology, including petrology and mineralogy. It may be limited to rocks found on Earth, or it may include planetary geology that studies the rocks of other celestial objects.

Rocks are usually grouped into three main groups: igneous rocks, sedimentary rocks and metamorphic rocks. Igneous rocks are formed when magma cools in the Earth's crust, or lava cools on the ground surface or the seabed. Sedimentary rocks are formed by diagenesis and lithification of sediments, which in turn are formed by the weathering, transport, and deposition of existing rocks. Metamorphic rocks are formed when existing rocks are subjected to such high pressures and temperatures that they are transformed without significant melting.

Soil, also commonly referred to as earth, is a mixture of organic matter, minerals, gases, water, and organisms that together support the life of plants and soil organisms. Some scientific definitions distinguish dirt from soil by restricting the former term specifically to displaced soil.

Soil consists of a solid collection of minerals and organic matter (the soil matrix), as well as a porous phase that holds gases (the soil atmosphere) and a liquid phase that holds water and dissolved substances both organic and inorganic, in ionic or in molecular form (the soil solution). Accordingly, soil is a complex three-state system of solids, liquids, and gases. Soil is a product of several factors: the influence of climate, relief (elevation, orientation, and slope of terrain), organisms, and the soil's parent materials (original minerals) interacting over time. It continually undergoes development by way of numerous physical, chemical and biological processes, which include weathering with associated erosion. Given its complexity and strong internal connectedness, soil ecologists regard soil as an ecosystem.

A desert is a landscape where little precipitation occurs and, consequently, living conditions create unique biomes and ecosystems. The lack of vegetation exposes the unprotected surface of the ground to denudation. About one-third of the land surface of the Earth is arid or semi-arid. This includes much of the polar regions, where little precipitation occurs, and which are sometimes called polar deserts or "cold deserts". Deserts can be classified by the amount of precipitation that falls, by the temperature that prevails, by the causes of desertification or by their geographical location.

Deserts are formed by weathering processes as large variations in temperature between day and night strain the rocks, which consequently break into pieces. Although rain seldom occurs in deserts, there are occasional downpours that can result in flash floods. Rain falling on hot rocks can cause them to shatter, and the resulting fragments and rubble strewn over the desert floor are further eroded by the wind. This picks up particles of sand and dust, which can remain airborne for extended periods – sometimes causing the formation of sand storms or dust storms. Wind-blown sand grains striking any solid object in their path can abrade the surface. Rocks are smoothed down, and the wind sorts sand into uniform deposits. The grains end up as level sheets of sand or are piled high in billowing dunes. Other deserts are flat, stony plains where all the fine material has been blown away and the surface consists of a mosaic of smooth stones, often forming desert pavements, and little further erosion occurs. Other desert features include rock outcrops, exposed bedrock and clays once deposited by flowing water. Temporary lakes may form and salt pans may be left when waters evaporate. There may be underground water sources in the form of springs and seepages from aquifers. Where these are found, oases can occur.

Karst (/kɑːrst/) is a topography formed from the dissolution of soluble carbonate rocks such as limestone and dolomite. It is characterized by features like poljes above and drainage systems with sinkholes and caves underground. There is some evidence that karst may occur in more weathering-resistant rocks such as quartzite given the right conditions.

Subterranean drainage may limit surface water, with few if any rivers or lakes. In regions where the dissolved bedrock is covered (perhaps by debris) or confined by one or more superimposed non-soluble rock strata, distinctive karst features may occur only at subsurface levels and can be totally missing above ground.

A mountain is an elevated portion of the surface of a planet, generally with steep sides that show significant exposed bedrock. Although definitions vary, a mountain may differ from a plateau in having a limited summit area, and is usually higher than a hill, typically rising at least 600 metres (2,000 ft) above the surrounding land. A few mountains are isolated summits, but most occur in mountain ranges.

Mountains are formed through tectonic forces, erosion, or volcanism, which act on time scales of up to tens of millions of years. Once mountain building ceases, mountains are slowly leveled through the action of weathering, through slumping and other forms of mass wasting, as well as through erosion by rivers and glaciers.

In geography and geology, a cliff or rock face is an area of rock which has a general angle defined by the vertical, or nearly vertical. Cliffs are formed by the processes of weathering and erosion, with the effect of gravity. Cliffs are common on coasts, in mountainous areas, escarpments and along rivers. Cliffs are usually composed of rock that is resistant to weathering and erosion. The sedimentary rocks that are most likely to form cliffs include sandstone, limestone, chalk, and dolomite. Igneous rocks such as granite and basalt also often form cliffs.

An escarpment (or scarp) is a type of cliff formed by the movement of a geologic fault, a landslide, or sometimes by rock slides or falling rocks which change the differential erosion of the rock layers.

An alluvial plain is a plain (an essentially flat landform) created by the deposition of sediment over a long period by one or more rivers coming from highland regions, from which alluvial soil forms. A floodplain is part of the process, being the smaller area over which the rivers flood at a particular time. In contrast, the alluvial plain is the larger area representing the region over which the floodplains have shifted over geological time.

As the highlands erode due to weathering and water flow, the sediment from the hills is transported to the lower plain. Various creeks will carry the water further to a river, lake, bay, or ocean. As the sediments are deposited during flood conditions in the floodplain of a creek, the elevation of the floodplain will be raised. As this reduces the channel floodwater capacity, the creek will, over time, seek new, lower paths, forming a meander (a curved path). The leftover higher locations, typically natural levees at the margins of the flood channel, will be eroded by lateral stream erosion, local rainfall, and possibly wind transport if the climate is arid and does not support soil-holding grasses. These processes, over geologic time, will form the plain, a region with little relief (local changes in elevation) yet with a constant but slight slope.

Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust and then transports it to another location where it is deposited. Erosion is distinct from weathering which involves no movement. Removal of rock or soil as clastic sediment is referred to as physical or mechanical erosion; this contrasts with chemical erosion, where soil or rock material is removed from an area by dissolution. Eroded sediment or solutes may be transported just a few millimetres, or for thousands of kilometres.

Agents of erosion include rainfall; bedrock wear in rivers; coastal erosion by the sea and waves; glacial plucking, abrasion, and scour; areal flooding; wind abrasion; groundwater processes; and mass movement processes in steep landscapes like landslides and debris flows. The rates at which such processes act control how fast a surface is eroded. Typically, physical erosion proceeds the fastest on steeply sloping surfaces, and rates may also be sensitive to some climatically controlled properties including amounts of water supplied (e.g., by rain), storminess, wind speed, wave fetch, or atmospheric temperature (especially for some ice-related processes). Feedbacks are also possible between rates of erosion and the amount of eroded material that is already carried by, for example, a river or glacier. The transport of eroded materials from their original location is followed by deposition, which is arrival and emplacement of material at a new location.