Fun Geography Encyclopedia: Fun Popular Science Series

Author: Liu Xingshi
Publisher:
Publish Date: 2005-11-01
Features: In life, people often mention rocks. But what exactly are rocks? Besides rocks, people also talk about minerals. Are rocks and minerals the same thing? No, rocks and minerals are two different things. The composition of rocks is much more complex than that of minerals. They are formed through special geological processes by aggregating many minerals or rock fragments. What geological processes form hard rocks? The force that forms rocks is "fire." Molten rock erupts onto the ground or remains underground. Both can solidify to form rocks. This type of rock is called igneous rock, and in the past, some people simply called it volcanic rock. The black basalt is formed by basaltic magma erupting onto the ground. Therefore, you can often see many air-filled pores inside it! Granite is formed by slowly cooling and solidifying underground. So it contains many well-crystallized minerals. The second force that forms rocks is "water." Exposed surface rocks gradually weather and break down, are carried by water to other places, and accumulate. Over very long geological eras, they transform into new rocks called sedimentary rocks, which were once called aqueous rocks. Mud becomes mudstone or shale, sand becomes sandstone, pebbles become conglomerate, and marine carbonate becomes limestone. The third force that forms rocks is "high temperature" and "high pressure." Existing rocks are buried underground and gradually change their properties under high temperature and pressure, transforming into a new type of rock called metamorphic rock. Igneous rocks that undergo metamorphism form primary metamorphic rocks, such as granite turning into gneiss. Sedimentary rocks that undergo metamorphism form secondary metamorphic rocks, such as mudstone and shale turning into slate and schist. Sandstone turns into quartz sandstone, and limestone turns into marble. There are all kinds of rocks, with all kinds of compositions and formation reasons. Don't get them mixed up.