Rocks and the Rock Cycle
Rocks are divided into three different groups which include Igneous, Sedimentary, and Metamorphic rocks, based on how they form. The way that geologist classify rocks is by their crystal size and color. You can tell which minerals it contains by its color but this is not the most reliable way because the color of the mineral can change. The more reliable way to identify the rock is by the size of the crystals or other particles they contain. Rocks get their texture by the size, shape and arrangement of the crystals, the texture where and how it was formed also the rock it is made from.
Igneous rock:
Igneous rock:
Intrusive rocks have larger crystals because the cool slowly, which gives the rocks a coarse-grained texture. Unlike extrusive rocks which cool slowly, Intrusive rocks cool very fast and it does not allow their crystals to grow much so for that reason is why they have a fine-grained texture.
Sedimentary rock is a rock that forms over time as sediment (small, solid pieces of material that comes from rocks or living organisms) is squeezed and cemented together. Sedimentary rocks are classified into three groups Clastic, Chemical and Organic rock. Clastic rock are sedimentary rocks that form from the broken fragments of other rocks which are usually held together by cement . These rocks are classified mostly by the average size of the fragments. When a rock contains gravel and pebbles its called conglomerate. Sandstone is made up of grains of sand. Mudstone is made up of mostly mud or silt. Chemical rocks are formed when minerals percipitate out of the solution. Rainwater dissolves minerals then the rainwater flows down rivers then it end up in the ocean. When the ocean evaporates the minerals remain in the ocean then the process of evaporation increases the concentration until the minerals percipitate out and sink to the ocean floor. Chemical rocks are also able to form on land. Organic rock is the last group if sedimentary rocks. These rocks form because of organic processes. Marine animals such as clams take calcium carbonate to form their shells and skeletons. When these animals die their shells fall to the bottom of the ocean floor and after a period of time they join together and become limestone, which is one of the most common types of sedimentary rocks.
Metamorphic rock is rock that has been changed by temperature, pressure or reactions with hot water, most are formed underground. The original rock that turns into a metamorphic can be any type of rock but after the metamorphism the rock has a different mineral content from the original rock. It also changes the the texture of the rock.
The rock cycle is a series of processes in which rocks continuously change from one type to another. The image below shows how the rock cycle goes.
Sedimentary rock is a rock that forms over time as sediment (small, solid pieces of material that comes from rocks or living organisms) is squeezed and cemented together. Sedimentary rocks are classified into three groups Clastic, Chemical and Organic rock. Clastic rock are sedimentary rocks that form from the broken fragments of other rocks which are usually held together by cement . These rocks are classified mostly by the average size of the fragments. When a rock contains gravel and pebbles its called conglomerate. Sandstone is made up of grains of sand. Mudstone is made up of mostly mud or silt. Chemical rocks are formed when minerals percipitate out of the solution. Rainwater dissolves minerals then the rainwater flows down rivers then it end up in the ocean. When the ocean evaporates the minerals remain in the ocean then the process of evaporation increases the concentration until the minerals percipitate out and sink to the ocean floor. Chemical rocks are also able to form on land. Organic rock is the last group if sedimentary rocks. These rocks form because of organic processes. Marine animals such as clams take calcium carbonate to form their shells and skeletons. When these animals die their shells fall to the bottom of the ocean floor and after a period of time they join together and become limestone, which is one of the most common types of sedimentary rocks.
Metamorphic rock is rock that has been changed by temperature, pressure or reactions with hot water, most are formed underground. The original rock that turns into a metamorphic can be any type of rock but after the metamorphism the rock has a different mineral content from the original rock. It also changes the the texture of the rock.
The rock cycle is a series of processes in which rocks continuously change from one type to another. The image below shows how the rock cycle goes.