Coasts 8 Markers (Excluding Formations Of Landforms) Flashcards
Explain how coastal landscape has changed over time, from millennia to seconds -LE
- Sediment transported to ND for over 30MN YEARS, gradually built up into delta. Takes long to build in a low energy environment.
- Gentle Med winds from W/NW leads to LSD, transporting sediment from distributary lobes to easterly direction. TAKES 100S of years to accumulate long barrier bars parallel to shore that enclose lagoons
- Lagoons fill with silt, forming salt marshes.
- Amount of sediment input by fluvial deposition changes bc of Monsoon season at source of Nile in Ethiopia. River had more energy to transport sediment.
- Additional sediment changes shape of delta, elongate lobes or barrier bars and change course of distributaries YEARLY.
- Pulse of discharge caused river to flood annually, leading to broken levees, which spreads new alluvial deposits in MINUTES.
Explain how the coastline has changed over time, from millennia to seconds. HE
Example of HE= N.YK COAST.
-200MN YEARS ago, chalk laid at the bottom of ancient ocean as diatoms. Overtime compressed to form sedimentary layers of chalk. Isostatic change meant chalk sedimentary rock revealed as headland (FLAMBOROUGH HEAD).
- 11,000 YEARS ago, last glaciation left glacial till which deposited on top of FH. Gave steep chalk cliff gentle slope on top.
- CENTURIES: Arch at North landing collapsed in 1984. Over DECADES, arch weakened as 2 vertical joints weathered by Freeze thaw and thermal expansion. Glacial till became heavier and more saturated, so arch became unstable.
- As result, in hours, landscape changed as storm destroyed arch in one night.
With reference to HE coast, explain how landforms can be interrelated (8)
-HEADLANDS & BAYS
*FH= Flamborough head
MINI INTRO: Saltburn to FH= 60km, dominant destructive waves from N & NE- 1500km fetch -> high rates of erosion at Saltburn & Kettleness. Geology=discordant coastline —> formation of Filey Brigg (headland) and Filey Bay.
- Headlands & bays formed at discordant headland. Soft rock erosion> hard rock. Wave refraction occurs at headlands -> waves elongate around bay, so slow down -> deposition of sediment at bay.
- H&B interrelated as w/o headlands and wave refraction, no sediment deposited at bay to create beaches.
- Filey Brigg acts as natural groyne as it breaks HE waves, allowing for deposition and accumulation of sediment at Filey Bay.
HE coast interrelated Q continued…
HEADLANDS AND CAVE/ARCH/STACK
EXAMPLE: GREEN STACKS PINNACLE
-Wave refraction can lead to formation of c/a/s and stumps.
- Cracks and faults in headlands exploited by HE waves.
-Friction increases when waves reach shallow water, increasing depth and shorter wavelengths.
-Continued wave erosion on sides of headlands -> formation of caves. Further erosion of caves enlarges cave, eventually to arch.
-Weathering & erosion widens and weakens the arch, and top heavier due to saturation etc, causes top to collapse, leaving stack.
- Material from this mass movement contributes to sediment input of coastal system.
- Eroded arch allows sediment transportation through opening.
-EXAMPLE = GSP surroundings FH.
With reference to LE coast, explain how landforms are interrelated (8)
NILE DELTA
LOBE & ONSHORE BAR
-Nile Delta-> LE coastline. Microtidal, small,low energy waves. Dep>Ero.
- Damietta and Rosetta distributaries have constant flow of water from Nile which carries sediment. Sediment deposited where kinetic energy is lost and accumulation —> LOBE
- Prevailing winds from NW encourages LSD, carrying sediment across the lobes —> SPIT
- SPIT grows and forms onshore bar connected to lobe and cuts of shallow body of water -> LAGOON.
EXAMPLE: BURULLUS LAGOON.
Explain the PHYSICAL factors which influence the formation of landforms in HE coastline
*PHYSICAL FACTORS:
-wind
-waves
-tides
-geology
GEOLOGY:
-Geology will likely influence the high energy
coastline through differences in rock resistance affecting the rates of erosion, weathering and mass movement. Differences in rock resistance as a result of rock structure, alignment and lithology. Decides layout of coast and what landforms occur. Includes type and chemical composition of rock and its arrangement on coast. Also impacts pH of surrounding water. Discordant v concordant. N.YK hard chalk, soft shale/clay. Glacial till on H.ness Coast and how lead to diff coastal landscapes.
WINDS:
-winds affect the waves arriving at the coastline through variations in their speed (friction w particles), direction and frequency. These will influence rates of geomorphic processes on different areas of the coastline. Wind also carries sand particles and hit cliff face at high speeds, contributing to erosion. Eventually weakens cliff face as small fragments of rock slowly chip away under constant barrage of miniscule projectiles.
WAVES:
-waves heavily involved in formation of erosional v depositional landforms. Depositional-constructive waves- deposit sediment and shingle up beach. Erosional-destructive waves-high energy- erode coastline and cliffs.-> Erosional landforms, mass movement when at base-> lots of sediment input into coastal system. TIDES ensure it is a constant process as change every 6 hours-regular.
Explain the PHYSICAL factors influencing the formation of landforms in a LE coast
- Nile Delta formed by fluvial and tidal currents depositing sediment at faster rate than waves and tide can erode.
- Formed when Nile river reaches Med sea, carrying large sediment load.
- Broad continental shelf margin at mouth of Nile, giving sediment platform on LE environments w low tidal ranges
- Cresentic Bars by Abu Qir headland associated with rip currents and small LSD
-Distributaries have created major lobes extending out front of delta - LSD and ocean currents carry eroded sediment to east along outer edge of delta —> spits/bars across burullus lagoon
-Limestone resistance to erosion causes headlands to form and wave refraction to occur.
