Question

question 48
2 pts
which of the following materials requires the lowest flow velocities to be entrained within flowing water?
gravel
clay
sand
silt
question 49
2 pts
erosion of what rock type is likely responsible for the black sand beaches of hawaii?
marble
granite
sandstone
basalt
question 50
2 pts

Explanation:

Question 48

To determine which material needs the lowest flow velocity for entrainment, we consider particle size and cohesion. Clay particles are very small (fine - grained) and often have cohesive forces between them. Gravel is large and requires high velocity. Sand and silt are larger than clay (in general, clay has the smallest particle size among these options) and less cohesive. So, clay can be entrained with the lowest flow velocity.

Hawaii has volcanic activity, and basalt is a dark - colored (black - to - dark - gray) volcanic rock. Marble is a metamorphic rock (from limestone), granite is a light - colored intrusive igneous rock, and sandstone is a sedimentary rock. The black sand beaches in Hawaii are formed from the erosion of volcanic rocks, and basalt is a common volcanic rock in Hawaii.

Answer:

B. Clay

Question 49