Have you ever wondered what happens when lava cools? Igneous rock forms, of course. The mantle of the Earth is very hot, but it remains solid because it’s under intense pressure. Sometimes, though, the pressure may ease. When this happens, the mantle melts and becomes magma, or hot, liquid rock. The magma cools slowly over millions of years and forms hard rock, such as granite. Rocks that form from magma are known as intrusive igneous rock because they form beneath the ground.
Igneous Rocks Facts For Kids
- Formed from cooled and solidified magma.
- Basalt and granite are common types.
- Can form above or below Earth’s surface.
- Those formed beneath the surface are “intrusive”.
- Those formed above the surface are “extrusive”.
- Granite is intrusive; basalt is extrusive.
- Pumice is so light it can float on water.
- Obsidian is volcanic glass, very sharp.
- Contain minerals like feldspar and quartz.
- The majority of Earth’s crust is igneous rock.
Magma
Igneous rocks, including varieties such as granite, basalt, and obsidian, are intriguing natural formations originating from magma, the molten material located beneath Earth’s crust. They are formed when this magma ascends to the surface and cools down, solidifying into rocks.
This process can occur either on the Earth’s surface, known as extrusive or volcanic igneous rock formation, or below the Earth’s crust, referred to as intrusive or plutonic igneous rock formation. Therefore, whenever you encounter these rocks, it’s fascinating to recall that they were once hot, liquid magma deep within the Earth!
Lava
Igneous rocks, intriguing formations originating from lava, are the solidified result of volcanic eruptions. During these eruptions, volcanoes expel hot, molten rock known as magma or lava. As this lava reaches the surface and cools, it hardens into what we know as igneous rocks.
Basalt and obsidian are two common examples of these rocks, the former prevalent in oceanic crust and the latter recognized by its glassy appearance. Therefore, encountering an igneous rock is akin to touching a tangible remnant of a volcano’s fiery history.
Basalt
Basalt, an intriguing igneous rock that captivates the interest of children, is created when lava from a volcanic eruption rapidly cools down. It typically sports a black or grey color scheme and exhibits a fine grain, indicating that the microscopic crystals within are minute and challenging to spot.
As the predominant rock in the Earth’s crust, basalt blankets almost the entirety of the ocean floor. Its exceptional hardness and durability make it an excellent choice for construction purposes. This is exemplified by its use in crafting some of the world’s most renowned statues and buildings, such as the Easter Island statues, demonstrating the practical application of this widespread rock.
Granite
Granite, an igneous rock, is formed through the lengthy cooling process of molten rock or magma deep beneath Earth’s surface – a process that takes millions of years, resulting in granite’s extreme hardness and durability.
The speckled appearance of granite, often seen in countertops or mountains, is due to the presence of various minerals such as quartz, feldspar, and mica. The black, white, and pink specks observed are the tangible remnants of these minerals that amalgamated millions of years ago to form the granite we see today.
Intrusive rocks
Intrusive igneous rocks, captivating geological formations that originate beneath the Earth’s surface, are the product of a unique and powerful process. This process begins when magma, a scorching liquid rock, gradually cools down and solidifies underneath the Earth’s crust. The leisurely pace of this cooling process facilitates the formation of large crystals, which endow intrusive rocks, such as granite, with their distinct coarse and grainy texture.
Due to their remarkable strength and durability, these rock types are commonly utilized in construction. Therefore, anyone who has laid eyes on a granite countertop or a robust, sizable building has witnessed the extraordinary outcome of the slow and potent process responsible for the formation of intrusive igneous rocks.
Extrusive rocks
Extrusive igneous rocks, an intriguing category of rocks, are created when magma from the Earth’s crust rises to the surface and swiftly cools, a process often triggered by volcanic eruptions. The swift cooling process doesn’t allow the minerals in the magma sufficient time to form large crystals, resulting in extrusive rocks generally having a fine or glass-like texture.
Basalt, a common extrusive igneous rock, is frequently used in construction and forms the Giant’s Causeway in Ireland, a natural marvel composed of thousands of basalt columns. So, when you spot a volcano, bear in mind that it’s a natural production unit for extrusive igneous rocks!
Volcanoes
Igneous rocks, intriguing geological formations, are intrinsically tied to volcanic activities and are birthed when either magma beneath the Earth’s surface or lava on the surface cools down and solidifies. Volcanic eruptions thus hold the potential for the creation of new igneous rocks.
These rocks come in various types, such as pumice, which is so light it can float on water, and others like basalt and obsidian which can be found globally, including in the chilled lava fields of Hawaii and Iceland. Therefore, any study of volcanoes should encompass an understanding of the remarkable igneous rocks they generate.
Crystallization
Igneous rocks, intriguing formations that come into existence through a process known as crystallization, are the product of volcanic eruptions. These eruptions discharge molten rock, or magma, which upon cooling and solidifying, forms igneous rocks either under the Earth’s crust or on its surface. The rate of cooling directly influences the size of the crystals within the rock, with slower cooling processes resulting in larger crystals, visible to the naked eye, as seen in granite.
Conversely, rapid cooling leads to the formation of minuscule crystals, like those in obsidian, which require a microscope for viewing. This transformation of magma into a solid state embedded with crystals exemplifies the process of crystallization.
Tectonic plate boundaries
Igneous rocks, as one of the three primary rock categories, are integral to the understanding of tectonic plate movements and interactions. These rocks are a byproduct of magma, molten rock located beneath the Earth’s crust, cooling and solidifying. They often emerge at the points where tectonic plates converge, caused by the intense heat and pressure in these areas.
For instance, when the plates separate or diverge, magma ascends to fill the void left, forming new igneous rocks. On the other hand, when the plates collide or converge, one plate may be compelled to submerge beneath the other and melt into magma, which could later cool down and form new igneous rocks. Consequently, the origination and positioning of igneous rocks can act as significant indicators of tectonic plate boundaries and their respective movements.
Silicate minerals
Igneous rocks, formed from the cooling and solidification of Earth’s magma, are an intriguing subject of study for children due to their composition predominantly of silicate minerals, the most abundant minerals on the planet. This preponderance of silicates, a combination of the two most prevalent elements in the Earth’s crust – silicon and oxygen, bestows upon many igneous rocks their distinctive colors and shapes.
For example, quartz, a common silicate mineral, can contribute to the appearance of an igneous rock, making it pink, white, or even translucent. Therefore, a shiny or vibrantly colored rock could very well be an igneous rock rich in silicate minerals!
Sometimes, the hot magma erupts at the Earth’s surface in the form of cracks, fissures or volcanoes. This hot rock is called lava. As the lava cools, it forms extrusive, igneous rock, such as basalt or pumice. Most igneous rocks are very hard because they were created under intense pressure and heat. Pumice is a soft, light rock that has many holes.
Fun Facts About Igneous Rocks for Kids
- The ocean floor is usually made of basalt rock, a hard, black, extrusive rock. Lava fields in Hawaii cool to form basalt rock.
- Rhyolite is similar to granite but it comes from volcanic lava. It is lighter in weight than granite, which is very dense.
- Sometimes igneous intrusions form underground in huge masses, known as batholiths. These batholiths can be 60 miles across.
- The Giant’s Causeway was made from a lava flow that erupted about 55 million years ago. As the lava cooled, it split and formed about 40,000 basalt pillars. The pillars look like huge stepping stones.
Igneous Rocks Vocabulary
- Igneous: made from molten rock (from the Greek word for fire)
- Mantle: the section of the Earth lying beneath the crust
- Magma: liquid rock beneath the Earth’s surface
- Lava: liquid rock that spews onto or near the surface of the Earth
- Intrusion: rock that forms under the ground
- Extrusion: rock that forms on or near the Earth’s surface
All About Igneous Rocks Video for Kids
This is the best video we found for kids to learn about the Igneous Rock:
Igneous Rocks Q&A
Question: Are igneous rocks useful?
Answer: People use igneous rocks in many ways. Granite counter tops are just one way. Obsidian, which is a very sharp, glass-like volcanic rock was used for tools or arrowheads.
