STRUCTURE OF THE EARTH
The structure of the Earth is divided into layers. These layers are both physically and chemically different. The Earth has an outer solid layer called the crust, a highly viscous layer called the mantle, a liquid layer that is the outer part of the core, called the outer core, and a solid center called the inner core.
Earth crust
Earth's crust is Earth's hard outer layer. It is less than 1% of Earth's volume. The crust is made up of different types of rocks: igneous, metamorphic, and sedimentary rocks.
Below the crust is the mantle. The upper part of the mantle is made up of peridotite, a rock denser than rocks common in the crust. The crust and the upper mantle make up the lithosphere. The lithosphere is broken up into tectonic plates that can move.
The crust is of two different types. One is the continental crust (under the land) and the other is the oceanic crust (under the ocean). The continental crust is thicker, and the oceanic crust is thinner. The thickness of the crust varies from 5 to 80 kilometres.
The temperature of the crust increases with depth because of geothermal energy. Where the crust meets the mantle the temperatures can be between 200 °C (392 °F) to 400 °C (752 °F).[1] The crust is the coldest layer because it is exposed to the atmosphere.
Composition of rocks
Igneous rocks make up over 90% of Earth's crust by volume.[2]p47 This is not noticeable because they are mostly covered by sedimentary and metamorphic rocks.
A single family of silicates, the feldspars, account for about half of the material in the crust (60% by weight), and quartz is a sizeable proportion of the rest. Other common minerals are mica and hornblende.
Only 8% of Earth's crust is non-silicate minerals, and this includes carbonates, sulfides, chlorides and oxides.
what is the igneous rock
Geological significance
Edit
The upper 16 km (10 miles) of the Earth's crust is composed of about 95% igneous rocks with only a thin, widespread covering of sedimentary and metamorphic rocks.[1]
Igneous rocks are geologically important because:
their absolute ages may be got from various forms of radiometric dating. This gives information about the dating of adjacent non-igneous geological strata;
their features are usually characteristic of a specific tectonic environment (see plate tectonics);
in some special circumstances they host important mineral deposits (ores): for example, tungsten, tin, and uranium are commonly associated with granites and diorites, whereas ores of chromium and platinum are commonly associated with gabbros.
Two types
Edit
Igneous rock occurs in two ways.
Igneous rock formed from magma that has become solid inside the earth is called intrusive igneous rock. Examples of intrusive igneous rock types are gabbro, diorite, and granite.
Igneous rock formed from lava that has become solid on the outside of the Earth is called extrusive igneous rock. This can happen because of the eruption of a volcano. Some extrusive igneous rock types are basalt, andesite, rhyolite, tuff, obsidian, and pumice.
Igneous rock is one of the three main rock types, the others being sedimentary and metamorphic rock.
Igneous rocks are rocks formed from molten magma. The material is made liquid by the heat inside the Earth's mantle.
When magma comes out onto the surface of the Earth, it is called lava. Lava cools down to form rocks such as tuff and basalt. Intrusive rocks are made when the magma slowly cools to form rocks under the surface. Granite is one of these.
Geological significance
The upper 16 km (10 miles) of the Earth's crust is composed of about 95% igneous rocks with only a thin, widespread covering of sedimentary and metamorphic rocks.[1]
Igneous rocks are geologically important because:
their absolute ages may be got from various forms of radiometric dating. This gives information about the dating of adjacent non-igneous geological strata;
their features are usually characteristic of a specific tectonic environment (see plate tectonics);
in some special circumstances they host important mineral deposits (ores): for example, tungsten, tin, and uranium are commonly associated with granites and diorites, whereas ores of chromium and platinum are commonly associated with gabbros.
Two types
Igneous rock occurs in two ways.
Igneous rock formed from magma that has become solid inside the earth is called intrusive igneous rock. Examples of intrusive igneous rock types are gabbro, diorite, and granite.
Igneous rock formed from lava that has become solid on the outside of the Earth is called extrusive igneous rock. This can happen because of the eruption of a volcano. Some extrusive igneous rock types are basalt, andesite, rhyolite, tuff, obsidian, and pumice.
The structure of the Earth is divided into layers. These layers are both physically and chemically different. The Earth has an outer solid layer called the crust, a highly viscous layer called the mantle, a liquid layer that is the outer part of the core, called the outer core, and a solid center called the inner core.
Earth crust
Earth's crust is Earth's hard outer layer. It is less than 1% of Earth's volume. The crust is made up of different types of rocks: igneous, metamorphic, and sedimentary rocks.
Below the crust is the mantle. The upper part of the mantle is made up of peridotite, a rock denser than rocks common in the crust. The crust and the upper mantle make up the lithosphere. The lithosphere is broken up into tectonic plates that can move.
The crust is of two different types. One is the continental crust (under the land) and the other is the oceanic crust (under the ocean). The continental crust is thicker, and the oceanic crust is thinner. The thickness of the crust varies from 5 to 80 kilometres.
The temperature of the crust increases with depth because of geothermal energy. Where the crust meets the mantle the temperatures can be between 200 °C (392 °F) to 400 °C (752 °F).[1] The crust is the coldest layer because it is exposed to the atmosphere.
Composition of rocks
Igneous rocks make up over 90% of Earth's crust by volume.[2]p47 This is not noticeable because they are mostly covered by sedimentary and metamorphic rocks.
A single family of silicates, the feldspars, account for about half of the material in the crust (60% by weight), and quartz is a sizeable proportion of the rest. Other common minerals are mica and hornblende.
Only 8% of Earth's crust is non-silicate minerals, and this includes carbonates, sulfides, chlorides and oxides.
what is the igneous rock
Geological significance
Edit
The upper 16 km (10 miles) of the Earth's crust is composed of about 95% igneous rocks with only a thin, widespread covering of sedimentary and metamorphic rocks.[1]
Igneous rocks are geologically important because:
their absolute ages may be got from various forms of radiometric dating. This gives information about the dating of adjacent non-igneous geological strata;
their features are usually characteristic of a specific tectonic environment (see plate tectonics);
in some special circumstances they host important mineral deposits (ores): for example, tungsten, tin, and uranium are commonly associated with granites and diorites, whereas ores of chromium and platinum are commonly associated with gabbros.
Two types
Edit
Igneous rock occurs in two ways.
Igneous rock formed from magma that has become solid inside the earth is called intrusive igneous rock. Examples of intrusive igneous rock types are gabbro, diorite, and granite.
Igneous rock formed from lava that has become solid on the outside of the Earth is called extrusive igneous rock. This can happen because of the eruption of a volcano. Some extrusive igneous rock types are basalt, andesite, rhyolite, tuff, obsidian, and pumice.
Igneous rocks are rocks formed from molten magma. The material is made liquid by the heat inside the Earth's mantle.
When magma comes out onto the surface of the Earth, it is called lava. Lava cools down to form rocks such as tuff and basalt. Intrusive rocks are made when the magma slowly cools to form rocks under the surface. Granite is one of these.
Geological significance
The upper 16 km (10 miles) of the Earth's crust is composed of about 95% igneous rocks with only a thin, widespread covering of sedimentary and metamorphic rocks.[1]
Igneous rocks are geologically important because:
their absolute ages may be got from various forms of radiometric dating. This gives information about the dating of adjacent non-igneous geological strata;
their features are usually characteristic of a specific tectonic environment (see plate tectonics);
in some special circumstances they host important mineral deposits (ores): for example, tungsten, tin, and uranium are commonly associated with granites and diorites, whereas ores of chromium and platinum are commonly associated with gabbros.
Two types
Igneous rock occurs in two ways.
Igneous rock formed from magma that has become solid inside the earth is called intrusive igneous rock. Examples of intrusive igneous rock types are gabbro, diorite, and granite.
Igneous rock formed from lava that has become solid on the outside of the Earth is called extrusive igneous rock. This can happen because of the eruption of a volcano. Some extrusive igneous rock types are basalt, andesite, rhyolite, tuff, obsidian, and pumice.







