Geology Chapter 10

Drainage basins = total area drained by stream and tributary. are separated by divides

Dendritic = develops on uniform rock, pattern resembling branches of trees. Most common pattern

Rectangular = regularly jointed rock. at 90 degree angles-ish.

Radial Pattern = forms on conical mountains

Trellis pattern = indicates erosion of folded sedimentary rocks. Parallel main streams w/short tributaries

What is the key factor in controlling sediment erosion, transportation and deposition? stream velocity

What factors affect stream velocity? Gradient, Channel shape and roughness, Discharge

Gradient = Slope of stream.

How does channel shape and roughness affect stream velocity? By increasing or lessening friction

Discharge = volume of water that flows past point in a unit of time

Streams erode by? Hydraulic action, abrasion, and solution

Hydraulic action = ability of flowing water to pick up and move sediments

Solution = dissolves rock and is absorped by water

Abrasion = grinding away of stream bed and its sediments

Stream transport sediments by? Bed load, suspended load, dissolved load

Bed load = large or heavy sediment particles travel on streambed

Traction = movement by rolling, sliding, dragging

Saltation = short leaps or bounces

Suspended load = sediment light enough to remain lifted above streambed

Dissolved load = soluble products of chemical weathering

potholes form by = abrasion of hard rock on streambed

Bars = from in middle of streams

Meanders are created when? a laterally eroding stream shifts across flood plain

River velocity are higher on the? Outside of curve

Natural levees are built by? beside streams by flood deposition

Delta forms when? stream flows into standing water

Alluvial fans forms? especially in dry climates, at the base of mountains as stream’s channel widens and velocity decreases

Downcutting = process of deepening valley by erosion of streambed

Graded stream = one with delicate balance between tis transproting capacity and its available load

Lateral erosion = the erosion and undercutting of stream’s banks

What widens a valley? lateral erosion

Headwater erosion = slow uphill growth of valley above its original source through gullying, sheet erosion

Stream terraces = form by erosion of rock or uplift. Cuts into old floodplain.

Incised meanders form as? 1.) river meanders are cut vertically downward following uplift 2.) Lateral erosion and downcutting