<span>During the stage of internal combustion engine operation in which the piston rises and compresses the fuel in the combustion chamber, the intake and exhaust valves will both be closed. This means that the mixture of fuel and air are compressed, due to the seal around the combustion chamber that has been created by the closure of both of these valves. Hopefully that answered your question for you!</span>
Water also moves underground, in the air, and moves in larger bodies of running water.
A rift valley is formed on a divergent plate boundary, which means that the two plates are
a. moving apart - this is the correct answer!
Rift valleys are often filled with lakes. For example, some scientists suggest that the Dead Sea lies in such a rift valley. Other such lake includes Lake Albert in Congo and Uganda.
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It changed so much because there were always European explorers heading out on voyages, for many reasons (like to trade with neighbouring countries, ferrying people from one land to the other, etc). During those voyages they found new lands, and so the maps had to be revised quite often because of these new discoveries.
