Ch. 16: Coastal Geomorphology Flashcards
Describe why oceans and coastlines are important when considering climate change and sea level change. Why is the Fraser River Delta vulnerable to sea level rise, when the rest of BC’s
coast is considered at low risk? You may need to consult your textbook for this one
-Oceans absorb vast amounts of CO2 from the atmosphere, acting as a critical buffer against climate change and helping regulate global temp
-And as global temp continues to rise due to climate change, glaciers and ice caps melt, which causes seawater to expand and sea level to rise. This rise threatens coastal communities, ecosystems, and infrastructure
Regarding Fraser River Delta vulnerability:
-The Fraser River Delta is at the mouth of the Fraser river, which is one of the largest rivers in BC. The delta is characterized by low-lying, flat terrain, making it susceptible to sea rise
Define salinity, brine, and brackish water. Explain what is meant by “water is the universal solvent.”
Salinity - measurement of dissolved solids per volume; expressed as parts per thousand
Brine - salinity is greater than 35 parts per thousand
Brackish water - salinity is less than 35 parts per thousands
Water coined as the “universal solvent” refers to the fact that:
-water dissolves more substances than any other liquid; most natural elements and compounds are found in world’s oceans and seas as dissolved solids
Describe the chemical composition and physical structure of the ocean.
Chemical structure:
-Composition of seawater is affected by atmosphere, minerals, bottom sediments, and living organisms
-elements such as chlorine, sodium, magnesium, sulfur, calcium, potassium and bromine account for 99% of dissolved solids in seawater
-Most common dissolved gases in seawater include CO2, N2, and O2
Physical structure:
-There are 3 main zones: mixing zone(2%), thermocline zone (18%), deep cold zone (80%)
-water is deep cold zone doesn’t freeze despite it being near 0°, due to the amount of salt content
-Temperature increases the deeper you go
-salinity near the surface varies, then stabilizes as you go deeper
-the dissolved gases have more complex profiles
Explain how oceans become more acidic and why we care about this issue.
-The CO2 the ocean absorbs from the atmosphere, forms carbonic acid in the seawater, which lowers the ocean’s PH value. Currently, its sitting at an avg PH of 8.2, but the PH could decrease to 0.4 to 0.5 by end of century
-We care because if changes to the ocean’s PH becomes too acidic, it could have very dangerous effects on marine life
In which oceanic zone do coastlines occur? How is this zone defined?
-Coastlines occur in the littoral zone
-Littoral zone is the region where the land meets the sea, that’s exposed to air at low tide and submerged at high tide
Describe the three main causes for sea level change.
-Climatic - thermal expansion of sea water
- Tectonic - processes like land subsidence, where parts of Earth’s crust sink downward, or uplift, where land rises upward
-Eustatic - sea levels changes due to changes in volume of ocean water
Explain what tides are in general, and describe the four main types of tides, paying special attention to the influence of the position of the Sun and the Moon. Why does the Bay of Fundy
experience such a dramatic tidal range?
-Tides are complex, twice-daily oscillations in sea level, ranging worldwide from barely noticeable to a rise and fall of several meters
-Flood tides - incoming rising tide that occurs twice a day; the tidal bulge rises when side of Earth spins toward moon or sun
-Ebb tides - falling tide that occurs twice a day; tidal bulge recedes as side of Earth spins away from moon or sun
-Spring tides - occurs when sun and moon are in alignment on same side of Earth; gravitational pull of sun and moon are compounding
-Neap tides - Occurs when sun and moon aren’t in alignment w/ earth; gravitational pull of sun and moon counteract
-The Bay of Fundy has a huge tidal range due to the tidal resonance; as the tide enters the narrow-shaped bay, it gets funneled through a progressively smaller area, which increases its height.
Describe wave motion at sea and near shore, and explain how coastal straightening occurs.
-The waves motions at sea is characterized by undulations of water generated by friction between wind and the ocean surface; at sea, the circular movement done is called swells, and they can range from small ripples to very large waves
-As the waves approach shore, it starts to change due to their interactions w/ the ocean floor. The orbiting tracks of water particles changes from a circular motions in deep water to more elliptical orbits in shallow water. This results in growing height and steepness w/ sharper wave crests. Point is reached where its height exceeds its vertical stability and crashes on shore, falling into a ‘breaker’ characteristic.
-Coastal straightening refers to the process by which irregular coastlines become straight overtime. This occurs due to the long-term effect of wave refraction, which concentrates wave energy on headlands, so therefore they receive the brunt of wave attack along a coastline, and different areas vary in erosion potential, straightening the coast overtime.
Explain how tsunami are different from typical swell waves, and describe their formation.
-Tsunamis are series of waves generated by large under sea disturbances, so they are produced by sudden, sharp motions in the seafloor caused by earthquakes, submarine landslides, or undersea volcanic eruptions
-They exceed 100 km in wavelength and are only a meter or so in height but once tsunami reaches shore, shallow water causes wavelength to shorten and wave height increases possibly up to 15 m or more
Explain where, geographically and geologically, coastal and erosional processes and landforms
tend to occur.
Erosional coastal processes and landforms occur along land of rugged, high relief, and that are tectonically active. Such as: coastlines of Pacific Ocean along North and South America
List the five main erosional coastal landforms and explain how they form. Be able to label them
on a diagram or photo.
-Sea cliffs - formed by undercutting action of sea; as indentations slowly grow at water level, sea cliffs become notched and eventually will collapse and retreat
-Wave-cut platforms - Form when wave action cuts a horizontal bench in the tidal zone as cliffs recede landward
-Sea caves - form on headlands or sea cliffs physical erosion along weakness in rock, like areas of less-resistant rock, fractures or faults
-Sea arches - form when further erosion of a sea cave on a coastal cliff creates a hole through the headlines
-Sea stacks - form when continued erosion of a sea cliff causes arches to collapse, leaving isolated columns of rock
List the six depositional coastal landforms and explain how they form. Be able to label them on a
diagram or photo. Are these static features?
-Barrier spit - made of material deposited in a long ridge extending from a coast, often partially crossing and blocking the mouth of a bay
-Bay barrier - forms when barrier spit grows to completely cut off a bay from the ocean
-Lagoon - shallow saltwater body cut off from ocean by bay barrier
-Tombolo -forms when sediment deposits connect shoreline w/ an offshore island or sea stack
-Beach - narrow strip along a coast where sediment is reworked and deposited by waves and currents
-Barrier beaches - long, narrow depositional features that form offshore roughly parallel to the coast
-Barrier island - broad, and extensive barrier beach
Define the two types of wetlands, and explain why these sensitive ecosystems are important to
protect.
-Salt marsh - made of holophytic (salt-loving) plants; usually form in estuaries and in the tidal mud flats behind barrier beaches and spits
-Mangrove swamp - form in tropical regions in intertidal areas; tolerant of saltwater abundance but intolerant of freezing temperatures
-These wetlands are important to protect because they are:
-great productive natural ecosystems that provide wildlife habitats
-natural reservoirs and erosion controllers
-They act as storm buffers
-natural sewage systems
