The core of planet Earth is protected by a hard outer layer known as the lithosphere. Life exists in the biosphere, where the hydrosphere (water), atmosphere (air), and lithosphere (ground) converge. As such, Earth’s lithosphere consists of rocks for the most part. These rocks come in all shapes, sizes, colors, and textures. However, sedimentary rocks are a unique kind. What makes sedimentary rocks unique is their formation and age. The oldest sedimentary rock dates back to 3.9 billion years ago, indicating that life existed in that period. In this article, you will learn their types and the characteristics of sedimentary rocks. Also, you will get to know the characteristics of metamorphic rocks.
1. What are Rocks? Types of Rocks
Rocks are the basic constituents of the Earth’s surface. They are concentrated and compact minerals with a homogeneous structure. They make up Earth’s crust, the outermost layer that separates the surface and the core.
The rocks available on Earth belong to three different types: igneous, metamorphic, and sedimentary rocks. These rocks are divided based on their origin and physical structure. (See What Is a Geode?)
2. What are 3 Types of Rocks?
Rocks on Earth are available in three distinct varieties. The three varieties are igneous, sedimentary, and metamorphic rocks. Characteristics of sedimentary rocks, igneous rocks, and metamorphic rocks differ from one another due to their varying properties. Their origins are just as different as their textures and structures.
- Igneous rocks: They form as a result of molten magma crystallization either above or below the Earth’s surface.
- Sedimentary rocks: Sedimentary rocks are what you get when loose solids become compact due to underground high pressure.
- Metamorphic rocks: Metamorphic rocks are just igneous and sedimentary rocks that have changed their form due to the high intensity of pressure and heat below the Earth’s crust. (See What are Geologic Features?)
3. What are Characteristics of Igneous Rocks?
Igneous rocks form when molten magma cools down and crystallizes. This magma usually makes its way toward the surface through volcanoes or fissures. When exposed to air, this magma solidifies to give rise to igneous rocks. Igneous rocks can be of two types depending on where they form:
- Extrusive igneous rocks are those forming above the surface.
- Intrusive igneous rocks are those forming under the surface. (See How are Volcanoes Distributed on the Map?)
4. What is the Texture of Igneous Rocks?
Due to variations in magma consistency and temperatures, the texture of igneous rocks is also variable. Igneous rocks have a texture that varies by size, age, and geographic location. However, igneous rock textures have two specific properties across all variations.
Igneous rocks have a generally crystalline or granular texture. Due to their formation process, the particles of igneous rocks have a tight interlocking structure. This molecular structure leads to the characteristic crystalline and granular texture. Must read what are physical features in Geography?
5. What are Characteristics of Metamorphic Rocks?
Metamorphic rocks are the rocks that change due to the internal conditions of the Earth. The two most common reasons are high temperatures and high pressure. Metamorphic rocks turn out in the form of various precious metals and minerals sought after today as they are reactive. Specifically, due to the mineral substance’s high reactivity to water, metamorphic rocks are usually hard. The process of metamorphosis, however, is considered irreversible. Also, check out how do Mountains affect dry areas like Nevada?
6. What is the Texture of Metamorphic Rocks?
Due to their formation under high heat and high pressure, the textural classification of metamorphic rocks has two classes. These two textures are foliated and non-foliated.
- The foliated kind has a rough, parallelly structured texture. Examples of this type include slate and phyllite.
- The non-foliated kind has a relatively uniform structure and a smooth texture. Examples of this type include quartzite and marble. Also, check out what does Fool’s Gold look like?
7. What are Characteristics of Sedimentary Rocks?
The characteristics of sedimentary rocks are unique due to their formation. Sedimentary rocks form when sediments, consisting of solid materials, get buried under the ground. When buried under the ground, the sediments get compressed by high amounts of pressure to form sedimentary rocks. It is from this process that the layered pattern, among the prominent characteristics, arises.
Sedimentary rocks make up about 75% of the Earth’s surface. They are soft and closely linked to the discovery of fossils. Organic matter sometimes gets caught in the sediments and shows up in the sedimentary rocks millions of years later. (See What makes up the Lithosphere?)
8. What is the Texture of Sedimentary Rocks?
Sedimentary rocks have a rough and grainy structure due to the compression of sediments. However, despite their texture, sedimentary rocks often appear uniformly layered, giving off the impression of a smooth, rocky texture. (See Where is Obsidian Found?)
9. Which Characteristic is most common in Sedimentary Rocks?
The most common characteristics of sedimentary rocks are their structures. The identifying feature of all sedimentary rocks is their layered structure. The visible layers on sedimentary rocks are what sets them apart from all the others. Sandstone, limestone, and shale are examples of sedimentary rocks. The layered format is noticeable through all these examples. Must read how convection current causes the Lithospheric Plate to move?
10. What Characteristic Property is mainly used to Categorize and Identify Sedimentary Rocks?
The classification of sedimentary rocks takes place based on texture, chemical structure, molecular structure, and the constituent material of the sediments. The Characteristics of sedimentary rocks are found in the form of :
- Clastic sedimentary rocks,
- Chemical sedimentary rocks,
- Biochemical sedimentary rocks, and
- Organic Sedimentary rocks. (See How Hot is Lava in Fahrenheit?)
11. What is the Rock Cycle?
Although each rock type is unique, its classification is never permanent. The rock cycle allows igneous, sedimentary, and metamorphic rocks to cross over from one category to the other. These transformations can occur due to a variety of factors:
- Biological or human activities,
- Tectonic processes, and
- The heat inside the Earth. (See What is the Difference between Oceanic Crust and Continental Crust?)
A combination of these factors enables processes such as sedimentation, erosion, and weathering. These processes, in turn, cause the change of one type of rock into another. It can both occur naturally or artificially through human activities. (Also read Where does Earth End and Outer Space Begin?)