Question

seafloor spreading

1. in the late 1950s, the geologist harry hess suggested the idea of sea - floor spreading as outlined below:

a. the valley at the center of the ridge was a _, called a _, in earths crust.
b. here, _, or _, from deep inside earth rises and fills the crack.
c. the ocean floor _ away from the ridge.
d. the rising magma _ and _ to form _ that replaces the ocean floor.
e. this means that new _ forms.

Explanation:

a. The valley at the center of the ridge is a rift valley, a crack in Earth's crust.
b. Magma, or molten rock, from deep inside Earth rises and fills the crack.
c. The ocean floor spreads out away from the ridge.
d. The rising magma cools and hardens to form new rock that replaces the ocean - floor.
e. This means that new oceanic crust forms.

Answer:

a. rift valley, crack
b. magma, molten rock
c. spreads out
d. cools and hardens, new rock
e. oceanic crust