Streams, rivers and landscape evolution

Q1: List and describe the parts of a stream system (5)? Watersheds: The water–collecting area of a stream or river system Divides: The division between two watersheds Rills: narrow surface depressions that channel overland water flow before it reaches tributaries Tributaries: smaller streams that carry water to a trunk stream Mouth: The end of a system where a trunk stream meets the ocean or another large body of water

Q2: How does stream velocity differ in different parts of a stream channel? (2). In a straight segment, velocity is slowest near the bed and on the sides and greatest in the center of the channel just below the surface In a curved segment, velocity is slowest at the inside of the curve and greatest at the outside of the curve

Q3: How do stream valleys obtain their distinctive V shape? (1). Valleys obtain their v shape by mass wasting of the slopes due to chemical weathering of exposed bedrock in humid temperate climates. (In arid climates, stream valleys tend to have steep walled canyons.)

Q4: Define the mechanisms by which streams erode their channels (3). Abrasion: the scouring of a stream bed by transported particles (most effective in swift-moving waters) Hydraulic lifting: erosion by water pressure (most effective when water is forced into fractures, dislodges sediment and large chunks of rx.) Dissolution: water dissolves soluble bedrock

Q5:Describe how superposed and antecedent streams develop (2). Superposed: an existing stream cuts down through subsequent layers of different rx types and strata. Even if they are rx that the stream would otherwise flow around. Antecedent: an existing stream cuts through rx as an entire region undergoes uplift while maintaining its original channel. It may sometimes cut a water gap through an existing ridge or mountain Both types of streams may appear the same.

Q6: List and explain 3 ways in which rivers transport sediments (3) Fine solid particles are carried as a suspended load (visible-causes water to look muddy) Large sand grains, stones, and boulders are transported as bed load along the bottom of a channel. Sand sized particles bounce along with a jumping motion called saltation. Larger particles are rolled along in a process called traction. Invisible dissolved ions carried in the river are called the dissolved load