Formation and characteristics of Volcanic Landforms (CSEC Geography)

Summary

In this video, the presenter explores the fascinating world of volcanic landforms, explaining both intrusive and extrusive types. Intrusive landforms, such as sills, dikes, batholiths, and volcanic plugs, are formed when magma cools within the Earth's crust, while extrusive landforms, like lava plateaus and shield volcanoes, are created when lava or ash is ejected onto the surface. The video delves into the characteristics of basic and acidic lava, how various volcanic features form, and how volcanic activity can alter landforms over time. It concludes by discussing the transformation of volcanic landforms through erosion and weathering, and the concept of dormant and extinct volcanoes.

Takeaways

• 😀 A volcano is a mountain or hill with an opening that connects the earth's interior to its surface, through which materials are ejected.
• 😀 Volcanic landforms are broadly categorized into intrusive and extrusive types.
• 😀 Intrusive volcanic landforms are formed when magma cools inside the earth's crust, while extrusive landforms are formed on the surface from lava and volcanic material.
• 😀 Examples of intrusive volcanic landforms include sill, laccolith, dike, batholith, and volcanic plug.
• 😀 Sills are horizontal layers of magma, while laccoliths cause the rock above them to arch upwards.
• 😀 Dikes are vertical or lateral masses of magma that cut across rock layers.
• 😀 Batholiths are large, dome-shaped masses of magma formed deep inside the earth's crust and often act as magma chambers.
• 😀 Extrusive landforms result from the cooling of lava and the accumulation of volcanic material, and they may include ash, cinders, bombs, and blocks.
• 😀 Lava comes in two types: basic lava, which is hotter and flows faster, and acidic lava, which is more viscous and flows slowly.
• 😀 Basic lava forms low, gentle structures like lava plateaus and shield volcanoes, while acidic lava forms steep, localized structures like acid lava domes and composite cones.

Q & A

What are the two main categories of volcanic landforms?

Volcanic landforms can be broadly categorized into two types: intrusive volcanic landforms and extrusive volcanic landforms.

How are intrusive volcanic landforms formed?

Intrusive volcanic landforms are formed when magma cools and solidifies inside the Earth's crust.

Can you explain the difference between a sill and a laccolith?

A sill is a horizontal mass of solidified magma between rock layers, while a laccolith is a mass of magma that causes the overlying rock to arch upward, forming a dome-like structure.

What is a dike, and how does it form?

A dike is a mass of magma that cools across the bedding planes in a vertical or lateral direction, often forming where magma flows through a joint or fault.

What is the role of a batholith in volcanic activity?

A batholith is a large, dome-shaped mass of solidified magma that forms deep within the Earth's crust and often serves as a magma chamber.

What distinguishes basic lava from acidic lava?

Basic lava has a lower silica content, is hotter, and flows more easily and quickly. In contrast, acidic lava has a higher silica content, is cooler, and flows more slowly, being more viscous.

Why does basic lava flow over longer distances than acidic lava?

Basic lava is more fluid due to its lower viscosity, which allows it to flow faster and travel over longer distances before solidifying. In contrast, acidic lava is more viscous and solidifies faster.

What is a shield volcano, and how is it formed?

A shield volcano is a large, low cone formed by the eruption of basic lava, which flows over long distances and creates gentle, broad slopes. These types of volcanoes are often found over hot spots.

What is a caldera, and how does it form?

A caldera is a large, basin-shaped depression that forms when the summit of a volcano collapses after an explosive eruption, often leading to the creation of secondary cones within the crater.

What happens to volcanic landforms over time?

Over time, volcanic landforms may change due to processes like erosion, weathering, and mass wasting. Volcanic eruptions can also cause existing structures to grow in size or collapse, leading to the formation of calderas. Additionally, extinct volcanoes may become subjected to further erosion, exposing intrusive landforms.