Question

study questions
find the answers as you read.

1. how did the invention of sonar contribute to information about the ocean bottom?
2. what are mid - ocean ridges, rift valleys, and trenches?
3. according to the theory of seafloor spreading, where and how does new crust form?
4. what evidence supports the theory of seafloor spreading?

Explanation:

1. Sonar sends sound waves to the ocean - bottom. The reflected waves provide information about depth, topography, and features.
2. Mid - ocean ridges are underwater mountain ranges, rift valleys are long, narrow depressions at ridges, and trenches are deep, narrow valleys on the ocean floor.
3. According to seafloor spreading, new crust forms at mid - ocean ridges. Magma rises, cools, and solidifies to create new crust.
4. Evidence for seafloor spreading includes magnetic striping on the ocean floor, age of rocks (younger at ridges), and the presence of mid - ocean ridges.

Answer:

1. Sonar sends sound waves to the ocean bottom. Reflected waves give info on depth, topography, etc.
2. Mid - ocean ridges are underwater mountain ranges; rift valleys are depressions at ridges; trenches are deep ocean - floor valleys.
3. New crust forms at mid - ocean ridges. Magma rises, cools, and solidifies.
4. Magnetic striping on ocean floor, rock age (younger at ridges), and mid - ocean ridges' presence support seafloor spreading.