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

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

  • A. Physical Geography

  • B. Hazards

  • C. Political Ecology

  • D. Environmental Perception

  • E. Landscape Studies

  • F. Energy and Resource Geography

Sandstone is an example of _____ ​​​​​​.

  • A. Sandy soil

  • B. Loamy soil

  • C. Clay soil

  • D. Igneous rock

  • E. Sedimentary rock 

  • F. Metamorphic rock

Which of the following isn't an example of metamorphic rock?

  • A. Schist

  • B. Quartzite

  • C. Gabbro

  • D. Marble

  • E. Slate

  • F. Serpentinite

Which of the following statements is false concerning metamorphic rock?

  • A. The are less dense than igneous and sedimentary rocks

  • B. They can be foliated or non foliated

  • C. They are crystalline in nature

  • D. They have a more coarse texture than their protolith

  • E. They may be formed from an older metamorphic rock

  • F. They are characterized with precious metals and stones

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



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

Lake Baikal - Len Academy

Lake Baikal is the deepest freshwater lake in the world. It is located in Siberia, and has a depth of 5,315 feet (1,620 meters)

River Nile is the world's longest river, reaching a length of 6,853km. It runs through the borders of 11 African countries. These are Egypt, Sudan, South Sudan, Ethiopia, Uganda, Democratic Republic of the Congo, Kenya, Tanzania, Rwanda, Burundi and Eritrea

The deepest place on Earth is the Mariana Trench in the Pacific Ocean. It has a dept of 11,034 meters (or 36,201 feet)

Japan has recorded the most earthquakes and is thereby considered as the world's most earthquake-prone country

The planets Jupiter, Saturn, Uranus and Neptune have no solid surfaces, but are rather made up of gases. For this reason, humans can never stand on them

Burg Khalifa - Len Academy

Burg Khalifa is the tallest building in the world (as at 2023). It is situated in Dubai and stands at over 2,700 feet

Pepto Bismol-colored Lake Hillier is a pink colored lake present in Australia

Pepto Bismol-colored Lake Hillier - Len Academy

Mount Everest is the highest point on earth with a height of 8,849 meters (29,032 feet). It is located between Nepal and Tibet, an autonomous region of China.

Mountain Everest is a symbol of relationship between Nepal and Tibet, and was named in the nineteenth century after George Everest, a former Surveyor General of India

A day on planet venus is longer than a year. This is so because it takes venus 243 'earth days' to spin round its axis (rotation), but takes 225 'earth days' to go around the sun (revolution).

In geography, understand that a day is reached when the planet makes a full spin or rotation round it's axis. However, a year is reached when a planet revolves fully around the sun

The Four Corners is a location in the United States of Ameria where one can stand in four states simultaneously (at the same time). The states are: Utah, Colorado, Arizona and New Mexico.

On the Four Corners, a person stands on the southwestern corner of Colorado, southeastern corner of Utah, northeastern corner of Arizona, and northwestern corner of New Mexico at once.


Notable points in Geography

Planets can be categorized based on their composition. These include:

1. Terrestrial or Rocky Planets: They are mercury, venus, earth and mars. They are called terrestrial or rocky planets for the following reasons:

  • They have a rocky and compact surface.

  • They have no rings around them.

  • They have a few natural satellites.

  • They rotate slowly around their axis.

 

2. Gas or Jovian Planets: They include jupiter, saturn, uranus and neptune. They have the following features:

  • They are called jovian planets because they are bigger in size when compared to earth.

  • They are composed mainly of hydrogen and helium gas, hence the name 'gas planets' or 'gas giants'.

  • They rotate rapidly.

  • They have many satellites.

  • They have rings around them.

Please read more on the classification of planets here.

Planets of the Solar System - Len Academy

The following rules are required for a body to become classified (or regarded) as a planet:

  • It must orbit the sun.

  • It does not orbit another planet. This means that it must not be a satellite.

  • It must have sufficient mass which accounts for its self-gravity.

  • It must assume a nearly round shape.

Please read on the planets of the solar system here.

Earth's atmosphere is extremely important for the survival of all its inhabitants. As a student, it is important you comprehend how the above functions of the atmosphere support life. The explanations below give credence to this fact.

When one moves further away from earth, the atmosphere becomes thinner until it disappears into the outer space. There is no atmosphere in space. For this reason, astronauts will always wear a spacesuit while carrying along their oxygen gas masks and canisters when in space.

People living on very high altitudes will likely experience a reduced amount of oxygen in the atmosphere. Such people survive because their bodily organs become adapted to survive in such conditions.

On mountain everest for instance, mountain climbers will need to carry oxygen canisters because lesser amount of oxygen is present on this mountain.

Please read more on the functions of the atmosphere here

The interface forming the boundary between two atmospheric layers are always named with a 'pause' at its end; for instance;

  • Tropopause: This is the interface or boundary between the troposphere and stratosphere.

  • Stratopause: Interface between the stratosphere and mesosphere.

  • Mesopause: Interface between the mesosphere and ionosphere.

  • Ionopause: Interface between the ionosphere and thermosphere.

The atmosphere surrounding the earth is layered. Each layer has its own characteristics although the boundaries between them are not clearly defined.

The image below shows the different layers of the atmosphere:

Layers of the Atmosphere - Len Academy

Please read more on the layers of the atmosphere here.