by streams of which there are three main types. Floodplains are the parts of river valleys that are covered with water during floods. Due to their seasonal nature, floods create stratified layers in which larger particles tend to settle nearer the channel and smaller particles settle nearer the edges of the flooding area. Alluvial fans are sedimentary areas formed by narrow valley streams that suddenly drop to lowlands and widen dramatically. Sedimentary in these types of deposits tend to be larger closer to the uplands and finer near the edges of the fan. Delta deposits, the third of type of alluvium, are finer sediments that are discharged from streams into lakes and eventually settle near the mouth of the river. Lacustrine Parent material deposited by a lake. Beach ridges may be present where ancient lakes once washed up sand. Lacustrine material is well sorted and fine-textured, having finer silts and clays. Soils formed from lacustrine parent material have low permeability in part because of this high clay content. Marine Ocean deposited parent materials, called marine sediments, are collections of material that have been carried by rivers and streams to the ocean and eventually sink to the bottom. Such materials can vary in texture. Gravity transported Colluvium or colluvial debris is the collection of large rock fragments that have traveled downslope by gravity. Wind transported Parent materials can also be transported by wind, there are three important types. Loess Silt sized sediments transported by the wind. Aeolian Sand sized particles transported by the wind typically as dunes. Volcanic Tephra The most common parent material coming from volcanoes is Volcanic Ash carried away by the wind and settling different distances from the volcano. Organic Organic deposits (or cumulose deposits) are developed in place from plant residue (for example sphagnum moss) that has typically been preserved by a high water table, or potentially due to another factor that slows decomposition. Climate and weathering Climate is generally considered the most important factor influencing physical and chemical weathering processes. Physical weathering is especially important during the early stages of soil development. Rock can be disintegrated by changes in temperature which produces differential expansion and contraction. Changes in temperature can also cause water to freeze. The forces produced by water freezing can be as great as 2.1 × 105 kPa, which can split rocks apart, wedge rocks upward in the soil, and heave and churn soil