Oceanography Week 5 Study Questions
What is meant by "marine snow"?
"Marine snow" is white deep-sea ooze that has been moved up by geological processes and can now be seen on land. It is calcium carbonate that accumulated above the CCD and is now visible on places such as mountain tops.
Why are some areas of the seabed altogether free of overlying sediments?
All ocean water has sediments, but there are some very rare areas where for some reason the sediment cannot settle on the bottom. Some reasons for these rare areas could be strong currents that carry away the sediment before it has time to settle, hot water that dissolves the sediment before it can settle, or just the youth of the area hasn't permitted it time to collect any sediment yet.
Why do all sea birds and all marine turtle come to land?
All seabirds and female marine turtles have to come to land to lay their eggs (to breed).
Why is Atlantic sediment generally thicker than Pacific sediment?
Atlantic sediments are generally thicker than Pacific sediments because most of the sediment deposited into the Pacific Ocean cannot reach much further than its continental shelves. The sediment is trapped in the peripheral trenches and does not reach the deep ocean basin. The Atlantic also has more carbonate ooze than the Pacific.
What is thought to control the timing of synchronous hatches of marine turtles?
Because the mother turtles all lay their eggs within a few days of each other, six weeks later the when the eggs hatch there will be millions of baby turtles racing to the ocean. The flood of baby turtles overwhelms the predators so most of the hatchlings will make it out to sea. Researchers think that the synchronous laying and hatching of the eggs is timed by the tides.
What organisms are the sources of the two types of ooze?
Calcareous ooze is from carbon-containing material, such as the shells of foraminifera, mollusks called pteropods, and algae called coccolithophores. Siliceous ooze comes from silicon-containing material, such as the hard parts of radiolarians and algae called diatoms.
Where does most of the "dust" come from that is deposited in the oceans?
Given its gigantic extension, the Sahara Desert is the main global source of atmospheric dust, but there are other important hotspots around the so-called dust belt. The Gobi Desert is the main dust source in Asia with transport reaching as far as the Hawaiian Islands. The sediment from these deserts is carried by the winds and deposited in the oceans.
What is IRD and where does it come from?
IRD stands for ice-rafted debris and it refers to sediment of any grain size that has been transported by floating ice and released into an aqueous environment; the ice acts as a raft, providing buoyancy to any debris included within it or on its surface.
How can past climate be inferred from studies of marine sediment?
Marine sediments can reveal information about past climate through measuring isotopes of oxygen in carbonate shells found in deep-sea sediment - telling us about changes in water and air temperature as well as volume of ice. There is other evidence in those microfossils that can tell us about ocean circulation, the marine biosphere, and upwelling, in order to fill in our picture of ancient climates. Stratigraphy can also give us information on climate.
What is a methane hydrate and why are they important?
Methane hydrates are formed by the anaerobic decomposition of sediment. When combined with water, they can make crystals. They are important because they are a large source of carbon dioxide. Fluctuations in climate could make that ice melt, causing that carbon dioxide to be released into the atmosphere and further exacerbate climate change. Methane hydrates can also serve as records of past carbon dioxide levels.
Why do land animals come to the coast?
Most often land animals come to the coast in search of food, usually as scavengers feeding on marine animals that have been beached.
Contrast Neritic and Pelagic sediment.
Neritic sediment is mainly terrigenous and accumulates around the coast of continents. Pelagic sediment is found in the deep sea and is largely biogenous. Pelagic sediment is also much finer (smaller) than neritic.
Why are most beach sands *mostly* composed of quartz grains?
Quartz is the one of the most common minerals in earth's crust because silica and oxygen are some of the most common elements in the crust. Quartz is also a hard mineral (7 on the MOH's hardness scale) and because it has no planes or weakness, making it harder to erode than other minerals. So, because sands are derived from the weathering and erosion of the land masses and their mountains, and because quartz is common in the continental crust and hard to erode, most beach sand is quartz.
Where is the thickest sediment in the ocean basins? Why?
Sediment is thickest in the ocean basins in the areas around the edges of continents. This is because continents provide lots of sediment in the form of runoff of small pieces of rock and other debris from land. Sediments are also thickest in the areas furthest away from spreading centers, because these areas are the oldest and therefore have had the time to accumulate the most sediment.
What sediment accumulates most rapidly? Least rapidly?
Terrigenous sediment accumulates the most rapidly and cosmogenic sediment accumulates the least rapidly.
What is the "challenge" of the coast?
The "challenge" is that the coast is constantly changing. It's an environment subject to rapid and extreme change due to the changing tides and frequent storms that affect wave strength, nutrient availability, and the degree of salinity. Organisms living in coastal environments have to be hardy and adaptable. It can also be challenging have offspring in these changing environments, so a lot of organisms have to travel further inland to lay their eggs in calmer waters or safer lands.
Thought Question: If you were a climate scientist wanting to use the chemistry of foraminifera tests to reconstruct past climate change would you propose recovering sediment cores from the Pacific or the Atlantic Ocean? Explain
The Atlantic because much of the Pacific does not contain carbonate sediment as it is below the CCD.
What is the CCD and how does it determine what sediment is deposited in the oceans?
The CCD is the depth below which there are no carbonate sediments, because below that point, the sediments are dissolved. This means that carbonate sediments are mainly found in shallow water, where the sea floor is still warm enough to allow them to exist.
Why are the Cliffs of Dover white?
The cliffs of Dover are white because of the "marine snow" on them. They are made of white calcareous chalk made mostly of sediment from foraminifera and coccolithophores.
What factor determines the size of sea bird colonies?
The key factor that determines the size and location of seabird colonies is the availability of food.
According to the video what is the primary reason walrus come to land.
The video claims that the primary reason walrus come to the land is to molt their outer layer of skin and take a break from having to converse their body heat in the icy cold waters they spend most of their lives swimming in.
What are the four (4) main types of ocean sediment and where do they come from?
There are four types of sediment: cosmogenous (from outer space), hydrogenous (created from chemical reactions in seawater), terrigenous (continents erosion and river runoff), and biogenous (from marine creatures).
What are the two types of biogenic sediment?
They are two main types of biogenic sediments: calcareous biogenous sediments, and siliceous biogenous sediments.
Why do Killer whales come to the coast and risk stranding themselves on the beach?
They come to hunt the pups of sea lions who are just learning to swim and therefore make easy targets for the whales.
What do the marine iguanas of the Galapagos, eat?
They eat seaweed. The smaller females stick to eating seaweed on the exposed rock faces above the water's surface, but the larger males will dive below the waves to get at the roots.
