The Rock Cycle
A particular rock may not always remain the same type. Igneous, metamorphic, and sedimentary rocks are transformed as they pass through the rock cycle. The rock cycle is the continuous transformation of rocks from one type to another within the geosphere. All rocks on Earth started as igneous rocks, approximately 4.6 billion years ago. Over time, forces from wind, water, heat, and pressure transformed these early rocks into sedimentary and metamorphic rocks.
Despite its name, the rock cycle is not a loop. Rocks can change from one form to another and back again. A better term would be the rock "recycle," because rocks are continuously recycled on Earth. According to the Law of Conservation of Matter, rocks and other materials are neither created nor destroyed. Instead, materials change form.
Volcanic Eruption Volcanic activity brings molten rock to the Earth’s surface through cracks in the Earth’s crust. Sometimes this occurs through an eruption, or magma oozes slowly through small cracks over time. When magma reaches the Earth’s surface we call it lava.
Igneous RockIgneous rock is formed when lava cools. This can happen rapidly like it would in a volcanic eruption or slowly like it would with seafloor spreading.
Igneous rock layers can be pushed deep into the earth by tectonic activity. There they are subject to great heat and pressure and over time will be transformed into metamorphic rock.
Some igneous rock may be pushed into the mantle. There, these rocks are subject to high temperatures and pressure, and will melt and become magma again.
Not all igneous rocks are pushed back into the earth. Some remain at the surface. Here they are subject to weathering and are broken down into sediment.
SedimentThere are multiple processes of both mechanical and chemical weathering that result in the breakdown of rocks into smaller fragments. These fragments of rock are called sediments. Agents of erosion pick up sediment and transport it to a new location where it is placed back on the ground. We call this process deposition.
Sediment may also be pushed back into the earth due to tectonic activity or be further broken down into smaller fragments of rock.
Sedimentary RockWhen layers of sediment are subject to pressure over time they are compacted and transformed into sedimentary rock.
Sedimentary rock may be broken down back into sediment, form metamorphic rock, or be pushed down into the earth by tectonic activity where it will melt and become molten rock.
Metamorphic RockMetamorphic rock is formed when sedimentary rocks, igneous rocks, or a combination of both are subject to years of great pressure and high heat. This causes the minerals and material that makes up these rocks to reorganize and become new rock.
Metamorphic rock can be broken down into sediment or pushed deep into the Earth through tectonic activity where it will be melted and become molten rock.
MagmaMagma is molten (melted) rock from the mantle layer of the Earth. Upper crustal layers are often pushed into the mantle layer during tectonic activity. Once in the mantle, the solid rock will melt. There are convection currents in the mantle that distribute heat. As a result, the molten rock is in constant motion. This motion causes movement of the Lithospheric plates, called tectonic activity.
Despite its name, the rock cycle is not a loop. Rocks can change from one form to another and back again. A better term would be the rock "recycle," because rocks are continuously recycled on Earth. According to the Law of Conservation of Matter, rocks and other materials are neither created nor destroyed. Instead, materials change form.
Volcanic Eruption Volcanic activity brings molten rock to the Earth’s surface through cracks in the Earth’s crust. Sometimes this occurs through an eruption, or magma oozes slowly through small cracks over time. When magma reaches the Earth’s surface we call it lava.
Igneous RockIgneous rock is formed when lava cools. This can happen rapidly like it would in a volcanic eruption or slowly like it would with seafloor spreading.
Igneous rock layers can be pushed deep into the earth by tectonic activity. There they are subject to great heat and pressure and over time will be transformed into metamorphic rock.
Some igneous rock may be pushed into the mantle. There, these rocks are subject to high temperatures and pressure, and will melt and become magma again.
Not all igneous rocks are pushed back into the earth. Some remain at the surface. Here they are subject to weathering and are broken down into sediment.
SedimentThere are multiple processes of both mechanical and chemical weathering that result in the breakdown of rocks into smaller fragments. These fragments of rock are called sediments. Agents of erosion pick up sediment and transport it to a new location where it is placed back on the ground. We call this process deposition.
Sediment may also be pushed back into the earth due to tectonic activity or be further broken down into smaller fragments of rock.
Sedimentary RockWhen layers of sediment are subject to pressure over time they are compacted and transformed into sedimentary rock.
Sedimentary rock may be broken down back into sediment, form metamorphic rock, or be pushed down into the earth by tectonic activity where it will melt and become molten rock.
Metamorphic RockMetamorphic rock is formed when sedimentary rocks, igneous rocks, or a combination of both are subject to years of great pressure and high heat. This causes the minerals and material that makes up these rocks to reorganize and become new rock.
Metamorphic rock can be broken down into sediment or pushed deep into the Earth through tectonic activity where it will be melted and become molten rock.
MagmaMagma is molten (melted) rock from the mantle layer of the Earth. Upper crustal layers are often pushed into the mantle layer during tectonic activity. Once in the mantle, the solid rock will melt. There are convection currents in the mantle that distribute heat. As a result, the molten rock is in constant motion. This motion causes movement of the Lithospheric plates, called tectonic activity.