Geography

Igneous rock explained with its types and textures

len Alfred Ajibola - 19th June, 2022 @ 04:09 PM

Topics in Geography

Environmental geography explained with its branches Igneous rock explained with its types and textures Characteristics of Igneous Rock What are Sedimentary Rocks? Formation and Types of Sedimentary Rock Characteristics of Sedimentary Rock Types and Characteristics of Metamorphic Rock Physical geography explained with its branches Geography Scheme of Work, SS1, First Term Geography Scheme of Work, SS1, Second Term Geography Scheme of Work, SS1, Third Term Classification and types of planets with their characteristics Planets of the solar system explained with their characteristics Functions of the Atmosphere Layers of the Atmosphere Solar System in Geography Composition of the Atmosphere Human geography explained with its branches What are metamorphic rocks? Formation of metamorphic rock?


Academic Questions in Geography

Please click here to see all Questions and Answers

Earth's distance from the sun is approximately _____ million kilometers.

  • A. 147

  • B. 85

  • C. 40

  • D. 220

  • E. 309

  • F. 400

Which of the following is not a branch of physical geography?

  • A. Economic Geography

  • B. Religious Geography

  • C. Social Geography

  • D. Resource Geography

  • E. Settlement Geography

  • F. Industrial Geography

Water resource geography is a branch under physiography.

  • A. True

  • B. False

With regards to ozone, which of the following is incorrect?

  • A. Ozone is a triatomic molecule

  • B. Ozone layer aids in preventing excess ultraviolet radiation from reaching the earth

  • C. Ozone is a natural greenhouses gas

  • D. Ozone comprises of oxygen molecules only

  • E. Ozone layer brings about a global warming on earth

  • F. Ozone is present in the stratosphere

The atmosphere makes the followings possible on earth except _____.

  • A. Photosynthesis

  • B. Respiration

  • C. Rain

  • D. Ultraviolet rays

  • E. Global communication

  • F. Weather

The interface forming a boundary between the stratosphere and mesosphere is termed _____.

  • A. Mesoface

  • B. Mesopause

  • C. Mesostart

  • D. Stratoface

  • F. Stratopause

  • F. Stratostart

Which layer of atmosphere is closest to the earth?

  • A. Thermosphere

  • B. Mesosphere

  • C. Stratosphere

  • D. Ionosphere

  • E. Troposphere

  • F. Exosphere

Argon makes up _____ percent of the atmosphere.

  • A. 0.93

  • B. 0.002

  • C. 0.0005

  • D. 0.00009

  • E. 0.00005

  • F. 0.036


Igneous Rock:

Igneous rocks are formed when molten substances below the earth surface cools and solidifies. These molten substances are called magma or lava. Magma can be derived from melting of existing rocks on the earth crust.


The solidification of magma into igneous rock may be below the earth's surface (intrusive) or on the earth's surface (extrusive), thus giving rise to the two types of igneous rock.

Please read the characteristics of igneous rock here.


Types of Igneous Rock

  • Intrusive Igneous Rock: These are igneous rocks that crystallizes below the earth’s surface. They generally cool slowly during the process of solidification and tend to produce large crystals.

    Intrusive igneous rocks can also be termed as plutonic igneous rock. Examples are gabbro, granite and pegmatite.


  • Extrusive Igneous Rock: They are igneous rocks that form when molten magma erupts on the earth's surface. The molten magma cools and solidifies quickly, giving rise to small crystals in the process. Sometimes, the molten magma cools so quickly, allowing no time for crystals to grow. This rapid cooling results in the formation of an amorphous glass.

    Extrusive igneous rocks are also referred to as volcanic igneous rocks. Examples are basalt, rhyolite and scoria.

Please read on metamorphic rock and its formation here.


The image below shows various examples of igneous rock.
Len Academy

Please read on sedimentary rock, its formation and types here.


Textures of Igneous Rock

The texture of an igneous rock is determined by its size, shape and crystal or grain arrangement. In this regard, popular opinion concerning igneous rock confirms that the size of mineral crystals making up the rock will give an indication to the rate at which the magma or lava solidifies into forming the rock.

Please read on the characteristics of sedimentary rocks here.


Below are the types of texture (based on crystal or grain size) present in igneous rocks. They are:

  • Aphanitic: They are fine (almost smooth) in appearance and are less than 1mm in size. In fact, the grains can't be seen with the naked eyes.

  • Phaneritic: They are fine coarse-grained crystal particles that are between 1mm - 10mm in size. The grains are visible with the unaided eyes.

  • Pegmatitic: They are coarse-grained particles with size greater than 10mm.

  • Pyroclastic: The crystals are seen as fragmented, angular grains during the eruption of magma. A typical example is the  volcanic breccia.

  • Porphyritic: They comprise of both finely grained and large crystals. The large crystals are termed phenocrysts.

  • Vesicular: The are very large grained crystals which contain sponge-like vesicles. An igneous rock with this feature is pumice.

  • Glassy: An example of igneous rock with glassy particle is obsidian. They have a glassy texture because the molten magma cools quickly such that there isn't sufficient time for the formation of mineral crystals.

Please read the types and characteristics of metamorphic rock here.


Meanwhile, understand that the size of mineral crystal may be affected by the type and volume of gases present in the magma (or lava) alongside other chemicals which ultimately forms the rock via its cooling and solidification.

Please read metamorphic rock and its formation here.

Consequently, larger crystals in the magma generally give rise to intrusive igneous rocks. Conversely, smaller crystals indicates the formation of extrusive igneous rocks since they solidify almost immediately on reaching the surface of the earth.

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Amazing facts in Geography

Pumice - Len Academy

Pumice is a rock that floats on water

There are more stars in space than there are grains of sand on a beach

Africa on the globe hemispheres - Len Academy

Africa is the only continent with land in all four hemispheres of the globe

Venus is the only planet that spins in a clockwise direction

Black holes aren't black. They only give off a dark glow because they are constantly consuming matter

The world's quietest room is located at Microsoft's headquarters in Redmond, Washington. This Microsoft's laboratory room measures a background noise of -20.35dBA; and that's a deafening silence

The universe has a color named cosmic latte

An earthquake is more likely to happen in Japan than any other country

Only 2 countries have the color purple in their national flag. Both countries are:

Nicaragua and Dominica

With 221,800 islands, Sweden is believed to have more islands than any other country in the world.


NOTABLE POINTS IN Geography

The atmosphere consists of gases that surround the entire surface of the spherical shaped earth. The compositions of these gases are as follows:

Composition of the Atmosphere -Len Academy

  • Nitrogen (N2): 78.09%
  • Oxygen (O2): 20.95%
  • Argon (Ar): 0.93%
  • Carbon(IV)oxide (CO2): 0.036%
  • Neon (Ne): 0.002%
  • Krypto (Kr): 0.001%
  • Helium (He): 0.0005%
  • Xenon (Xe): 0.00009%
  • Hydrogen (H2): 0.00005%
  • Water Vapour: Variable

All of these gases (listed above) make up the atmosphere and are generally called air.

Please read more on the atmosphere and it's composition here

Human Geography focuses on the study of human beings, their origin, race, and how they are affected by the earth.

Human geography can be divided into the following branches:

  • Economic Geography: This aspect of human geography looks into the distribution of goods and services. Distribution of wealth across the globe is also considered here.

    Instances of economic geography include a study or research done on the richest nations on earth. During thus research, the processes accounting for their wealth are ascertained.


  • Religious Geography: It studies the origin and spread of religious groups including their beliefs.

    Instances of religious geography include the study of the Christian or Islamic religion as seen in documentaries.


  • Medical Geography: It studies the processes and events that bring about diseases and epidemics with regards to their geographical location, origin and distribution.

    As an instance, you may have heard about the geographical study and distribution of the disease 'COVID-19'. (Coronavirus is a case study here).

    Please read more on the branches of human geography here.

We have 3 main types or classes of rock based on how they are formed. These are:

1. Igneous Rock

Igneous Rock - Len Academy

 

2. Sedimentary Rock

Sedimentary Rock - Len Academy

 

3. Metamorphic Rock

Metamorphic Rock - Len Academy

Igneous rocks are formed when molten substances below the earth surface cools down and solidifies. These molten substances are called magma or lava. Magma can be derived from melting of existing rocks on the earth crust.

The solidification of molten magma into igneous rock may be below the earth's surface (intrusive) or on the earth's surface (extrusive), giving rise to the two types of igneous rock.

  • Intrusive Igneous Rock: These are igneous rocks that crystallizes below the earth’s surface. They generally cool slowly during the process of solidification and tend to produce large crystals.

    Intrusive Igneous Rocks are also referred to as plutonic igneous rocks. Examples are gabbro, granite and pegmatite.

  • Extrusive Igneous Rock: They are igneous rocks that form when molten magma erupts on top of the earth's surface. They cool down and solidify quickly, producing small crystals in the process. Sometimes, the molten magma cools so quickly, allowing no time for crystals to grow. This rapid cooling results in the formation of an amorphous glass.

    Extrusive Igneous Rocks are also referred to as volcanic igneous rocks. Examples are basalt, rhyolite and scoria.

Sedimentary rocks amount to about 76% of the earth's surface. They can be formed in different ways. These are:

  • By the deposition of the weathered remains of pre-existing rocks and their subsequent transportation and deposition. Sedimentary rocks formed in this way are known as clastic sedimentary rock.

  • By the accumulation and lithification of sediment or detrital rock.

  • By their precipitation from solution. Sedimentary rocks formed in this way are known as chemical sedimentary rock.

  • As a result of biogenic activities. Sedimentary rocks formed in this way are known as organic sedimentary rock.

Please read more on types of rocks here