Answer:
Explanation:
C is a volcano.
A volcano is as a result of igneous activities.
Volcanoes are landforms formed by the extrusion of magma on the earth crust.
Magma that reached the crust is called a lava and it is made up of molten rock minerals.
When the lava cools, it forms the rocks we see on the crust.
The mechanism by which minerals forms in a melt is known as differentiation. Differentiation is the process by which minerals separates from an originally uniform mixture. As temperature varies within the earth, new minerals forms by combining elements and others are broken down.
In a Volcano, the melt is the mineral soup. The melt is at a very high temperature. As it rises through the vent to the surface, temperature decreases very rapidly. When temperature reduces rapidly, it is difficult for large minerals to form. Minerals crystallise out of the melt according to the Bowen's reaction series and the composition of the melt.
We must note that, as the melt rises through the crust, it assimilates some crustal materials. Some of these materials can change the original composition of the melt as it rises. If such a melt orginates from the mantle, it mixes with crustal rocks and forms a rock bearing some mafic and felsic minerals.
It is typical to find fine grained rocks that lacks crystals in such a place. This is because the cooling of the melt was rapid and crystals could not form properly.
