Question

which discovery did scientists make at mid - ocean ridges that caused them to conclude that new rock was being formed by molten material? magnetic banding pillow - shaped rocks older rocks farther from the ridge rocks with similar characteristics

Explanation:

Pillow - shaped rocks are formed when molten material (lava) erupts underwater. As the lava comes into contact with the cold ocean water, it cools rapidly. The outer layer solidifies first, and the still - molten interior causes the rock to bulge, creating the pillow - like shape. This is direct evidence of new rock formation from molten material at mid - ocean ridges.
Magnetic banding is related to the Earth's magnetic field reversals as new rock forms and records the magnetic orientation at the time of its formation, but it is not the most direct evidence of new rock from molten material.
Older rocks farther from the ridge is more about the concept of seafloor spreading (new rock forms at the ridge and moves away over time), but it is not as direct an evidence of new rock from molten material as pillow - shaped rocks.
Rocks with similar characteristics could be due to various geological processes and is not a specific evidence of new rock formation from molten material at mid - ocean ridges.

Answer:

pillow - shaped rocks