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Homework answers / question archive / Question 1 1 / 1 pts If the earth is very old (about 4
Question 1
1 / 1 pts
If the earth is very old (about 4.5 billion years), why can't scientists study sea floor that is older than 200 million years?
Sea floor is subducted and destroyed over time
Most scientific information is lost due to the depth and pressure experienced at the sea floor
Very old sea floor is too deep to study
Traditional dating techniques do not work on sea floor sediments
1 / 1 pts
Calcareous oozes can originate from the biological activities of:
Radiolarians
Diatoms
Whales
Coccolithophorids and foraminiferans
Coccolithophorids and foraminiferans are microorganisms of the plankton. The hard parts of their bodies are made of calcium carbonate and when they die, these parts accumulate over the bottom of the ocean, forming calcareous oozes. Chapter 5, p. 141
1 / 1 pts
Why is calcareous ooze generally absent on the sea floor at depths greater than about 4500 meters?
Strong deep-water currents sweep sediments from these deeper areas to shallower basins
Calcium carbonate-producing organisms only live in water that is relatively shallow and near shore
Below that depth the water is more acidic and calcium carbonate is also more soluble in the cold water under pressure
Below that depth, land-derived sediments dominate and prevent the settlement of calcium carbonate
1 / 1 pts
Which type of sediment is most common on the continental shelf?
Biogenous
Hydrogenous
Terrigenous
Cosmogenous
1 / 1 pts
What does Earth's magnetic field do for us?
Maintains the 23.5 degree tilt of the axis
Shields us from harmful cosmic rays
Retails solar heat
Holds in the atmosphere
1 / 1 pts
What type of sediments are more common on the deep sea floor far from shore?
Biogenous
Terrigenous
Cosmogenous
Hydrogenous
1 / 1 pts
What type of ooze is most common in the deep-ocean basins surrounding Antarctica?
Radiolarian ooze
Diatom ooze
Calcareous ooze
Basaltic ooze
Information can be found in the section Pelagic Sediments Vary in Composition and Thickness.
1 / 1 pts
Sediments can store historical records about changes in ocean and atmospheric circulation as well as changes in the temperature of surface and deep water.
True
False
1 / 1 pts
Injection wells are used to extract core samples of marine sediments on the deep ocean floor.
True
False
1 / 1 pts
What do scientists look for in marine sediments if they want to study past changes in Earth's magnetic field?
Magnetite
Quartz
Volcanic dust
Basalt
4 / 4 pts
Match the sediment type on the left with its source on the right.
Terrigenous
Biogenous
Hydrogenous
Cosmogenous
1 / 1 pts
What is siliceous (silica-containing) ooze formed from?
Formainifera and coccolithophores
Radiolarians and diatoms
Dinoflagellates
Krill and other arthropods