Marine Transportation + Deposition: Sediment Sources + Characteristics

Question 1

What are the different types of sediment sources?

Answer 1

• rivers
• cliff erosion
• wind
• glaciers
• offshore areas
• longshore drift

Question 2

How are rivers a sediment source?

Answer 2

• most sediment in coastal zone results from river inputs, esp. in high-rainfall envi.s w sig. river erosion
• sediment may be deposited in estuaries (salty areas where rivers flow into sea) + then transported throughout coastal system by waves, tides + currents

Question 3

How is cliff erosion a sediment source?

Answer 3

• v important in areas w uncompacted (unstable) cliffs that are easily eroded
• coastlines may retreat up to 10m/yr, providing a sig. sediment input
• most erosion occurs during winter months bc more frequent storms

Question 4

How is wind a sediment source?

Answer 4

• coastal energy source + can cause sand to be blown along or up a beach
• sediment transported by winds may occur where there’s sand dunes or in glacial + desert envi.s, providing sediment inputs

Question 5

How are glaciers a sediment source?

Answer 5

• in some coastal systems (e.g. Antarctica), glaciers flow directly into ocean, depositing sediment stored in ice
• occurs when glaciers calve (ice breaking off glacier)

Question 6

How are offshore areas a sediment source?

Answer 6

• sediment transferred to coastal zone when waves, tides + currents erode offshore sediment sinks (e.g. offshore bars) + transport sediment onto beach, helping to build it up
• storm surges/tsunami waves may transfer sediment into coastal zone

Question 7

Describe the process of longshore drift. (how it acts as a sediment source)

Answer 7

• waves hit beach at an angle determined by direction of prevailing wind
• waves push sediment in this direction + up beach in swash
• wave then carries sediment back down beach in backwash, due to gravity
• over time this moves sediment along beach

Question 8

What is an e.g. of longshore drift (LSD)?

Answer 8

• 2018: LSD caused the Pohoiki Boat Ramp in Hawaii to be blocked off when the Kilauea volcano erupted
• volcanic material was transported along coastline by LSD, leading to deposition + beach formation. It formed a spit off the breakwater, eventually blocking entire boat ramp.