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

Biology

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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

 

 

Question 2

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

 

Question 3

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

 

 

Question 4

1 / 1 pts

Which type of sediment is most common on the continental shelf?

  

Biogenous

   

Hydrogenous

   

Terrigenous

   

Cosmogenous

 

 

Question 5

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

 

 

Question 6

1 / 1 pts

What type of sediments are more common on the deep sea floor far from shore?

  

Biogenous

   

Terrigenous

   

Cosmogenous

   

Hydrogenous

 

 

Question 7

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.

 

Question 8

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

 

 

Question 9

1 / 1 pts

Injection wells are used to extract core samples of marine sediments on the deep ocean floor. 

  

True

   

False

 

 

Question 10

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

 

 

Question 11

4 / 4 pts

Match the sediment type on the left with its source on the right. 

Terrigenous

 

               Land erosion, volcanoes, dust             

Biogenous

 

               Shells and skeletons of tiny plants and animals             

Hydrogenous

 

               Minerals that precipitate directly from seawater             

Cosmogenous

 

               Interplanetary dust, asteroids, and comets             

 

Question 12

1 / 1 pts

What is siliceous (silica-containing) ooze formed from?

  

Formainifera and coccolithophores

   

Radiolarians and diatoms

   

Dinoflagellates

   

Krill and other arthropods