(a) What is volcanic intrusion ?
(b) Describe the characteristics and mode of formation of a block mountain.
(c) List three landforms that are associated with intrusive volcanic activities.
(a) Meaning of Volcanic Intrusion: Volcanic intrusion occurs when the magma cools and solidifies within the earth's crust..
(b) Characteristics and Mode of Formation of a Block Mountain: Also called a. horst - occurs mostly in areas of intensive tectonic activities-Surface could.be flat -surface could be slightly tilted- Made of hard rocks-Modest In size -Steep-sided- Devoid of peaks -Can become irregular due to erosion and action of rivers -Bordered by, two parallel faults - Bordered by lowlands -Lowlands can be basins or rift valleys- Stand out above/the general level -Examples are Black Forest and Vosges in France, Harz mountain in Germany, Ruwenzori Mountain in Uganda, Hunsruck Mountain in Germany, etc.
Mode of Formation:- -Formed in areas of intensive tectonic activities -Earth movements bring about cracks/faults - Cracks/faults may be more than one -Crusted layer is broken into blocks- cracks/ faults can develop in parallel forms- If faults are of normal types-Tensional forces set in -May result in the central part standing while the flanks' pull apart and subside -This leaves behind the central blocks standing as block mountain-Alternatively when the faults are of reverse or thrust types -Compressional forces may set in -they, force the flanks over the central block- the central block subsides to form a rift valley- The flanks rise to form block mountains.
(c) Landforms that are Associated with Intrusive Volcanic Activities:-Dykes-Sill -Laccolith -Phacolith -Lopolith -Batholiths -Stock or bosses.
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