Scientists learn about the layers deep within the Earth's crust by studying how seismic waves travel ... Usually, they use seismic waves, which are waves generated by earthquakes
FOR MORE EXPLANTION...JUST A LITTLE MORE
NOT REALLY REQUIRED BUT YOU CAN USE JUST FOR YOUR REFERENCE..
Excellent question! Scientists use waves to study the different layers of the earth. Usually, they use seismic waves, which are waves generated by earthquakes or nuclear-test explosions. The seismic waves are bent, sped up, or slowed down, or even reflected when they pass through the earth's layers. Different types of materials (liquid vs. solid, rigid vs. softer) determine the speed of the waves. Bending of the waves occurs at the layer's boundaries. So, scientists study the path and speed of these waves through the earth to decipher boundaries and the materials that make up the layers.
THATS WITH QUESTION 1
Now 2
Most active divergent plate boundaries occur between oceanic plates and exist as mid-oceanic ridges. Divergent boundaries also form volcanic islands which occur when the plates move apart to produce gaps which molten lava rises to fill.
I hoped this helped...
~♥ ashlynn
Hey!
Hope this helps...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
A user mentioned in the comments of one of the answers deleted: "its B" < The user (<span>lolbae0806) had mentioned this...</span>
So I believe the correct answer is:
B.) More oxygen gas became present in the atmosphere.
Answer:<em>Chemical reaction, a process in which one or more substances, the reactants, are converted to one or more different substances, the products. Substances are either chemical elements or compounds. A chemical reaction rearranges the constituent atoms of the reactants to create different substances as products.</em>
Explanation:
Pressure decreases due to there being less gas above you
