Which of the following can you assume about the layers in areas 2 and 4?
a. the layers were originally horizontal.
b.
the layers were deposited in a river bed.
c.
the layers formed from sand dunes.
d.
the layers formed in a marine environment.

the answer is a i just took the test and a is correct the 1st question answer is What does an unconformity in a sequence of rock layers reveal about geologic history?  

A.

A rock layer must have turned upside down.

B.

A layer of rock might have eroded.

the answer is b

a mid-ocean ridge or mid-oceanic ridge is an underwater mountain range, formed by plate tectonics. this uplifting of the ocean floor occurs when convection currents rise in the mantle beneath the oceanic crust and create magma where two tectonic plates meet at a divergent boundary.a geomagnetic reversal is a change in a planet's magnetic field such that the positions of magnetic north and magnetic south are interchanged.