A ________ is a geographic low, which marks the location where oceanic lithosphere descends into the mantle.
A) fold and thrust mountain
B) deep-ocean trench
C) seismic zone
D) mid-ocean rift
Question 2
In the mid-twentieth century, researchers dredging the seafloor could not find any materials older than ________.
A) 10,000 years
B) 1.2 million years
C) 180 million years
D) 1.5 billion years