Question

Grade 1.2 Directions: Read pages 478.-481 and answer the folowing 1. How were the oceans first formed? 2. What percentage of the Earth's surface is covered with oceans? 3. Where does the salt in saltwater come from? 4. Look at Figure 17-3. What percentage of the ocean water are salts? 5. What is the name of the salt we use on our food? 6. 7.Is the overall level of ocean salinity constant? is the measure of the amount of solids dissolved in seawater.

Answer 1

1- The oceans have been formed from the riffing of the continental mass. After rifting small seas form first like the red sea now. With continuous divergence these small seas convert into large ocean like Pacific and Atlantic. But the water on the earth's surface come from the degassing of elements from the mantle.

2- Nearly 71 percent of the earth's surface is covered by the ocean.

3- Due to the weathering of the silicates the elements like Na, Cl goes to the river. As the river mixes with the ocean so these elements mix with the ocean to increase the salinity.

4- Generally we have 35 parts per thousand salts in ocean water.

7- Yes we can generalise that salinity of every ocean is same but it varies from 31 to 38. Dead sea is having the highest salinity.