Question

Read the given passage and answer the following questions.

We have already learnt that the temperature inside the earth goes on increasing with the increasing depth. It becomes so high that it melts the rocks to form the molten magma. Being bad conductor of heat, they trap the heat and continue to melt to add to the volume of the magma. The formation of magma is accompanied with the formation of gases and steam which tend to expand and rise. The magma and gases find their escape to the earth’s surface through the weak points in the earth’s crust. These weak points are usually provided by the tectonic plate boundaries. The tectonic plates are constantly moving since they are placed on the molten magma. When the two plates diverge away from one another, they create a gap, also called the fault which provides an escape to the hot gases and magma to come out on the earth’s surface through the eruption of volcano. A volcano may also erupt when two plates converge, especially if one is continental plate and the other is an oceanic plate. The oceanic plate being denser than the continental plate subsides below the continental plate. It gets thrust into the mantle, where it may melt, form magma and then escape to the earth’s surface through the plate margin called the fault.

1. Why does the temperature inside the earth increase with increasing depth?
2. Establish the correlation between hot interior of the earth and the phenomena of volcanoes.
3. What role do the tectonic plate boundaries play in the phenomena of volcanoes?
4. Do you think the volcanoes would have erupted if there were no plate boundaries? What would have been the consequences of that?

Answer 1

1. The temperature inside the Earth increases with increasing depth because the deeper layers trap heat due to the poor heat conductivity of rocks. This results in the temperature rising so high that rocks melt to form molten magma. The heat is also generated and retained due to the intense pressure and radioactive decay processes inside the Earth. The increasing temperature gradient with depth is about 1°C increase per 32 meters of depth approximately.
2. The hot interior of the Earth causes rocks to melt and form magma. This molten magma, along with gases and steam, tends to expand and rise because gases try to expand. These materials escape to the surface through weak spots in the Earth’s crust. This movement and eruption of magma and gases through faults and cracks results in the phenomena of volcanoes. Thus, the hot interior directly leads to the formation and eruption of volcanoes as the magma escapes to the surface.
3. Tectonic plate boundaries act as weak points or fault lines in the Earth’s crust. Because the plates are constantly moving on molten magma, when they diverge (move apart), they create gaps or faults that allow magma and gases to escape to the Earth’s surface leading to volcanic eruptions. Similarly, when two plates converge, especially when an oceanic plate subducts beneath a continental plate, the oceanic plate melts in the mantle and magma rises through the faults at the plate margin causing volcanoes. Therefore, tectonic plate boundaries provide the escape routes for magma and gases, making them crucial to volcano formation and eruptions.
4. Without plate boundaries, volcanoes would likely not have erupted. This is because the primary escape routes for magma and gases are the faults and weak points created by tectonic plate movements. Without faults, the magma would remain trapped beneath the crust, increasing pressure and heat. This could cause extremely high pressures to build up, potentially leading to catastrophic underground explosions or the formation of large magma chambers, but not typical volcanic eruptions. The absence of plate boundaries would thus prevent the regular release of magma and gases. This might lead to increased geologic pressure and instability but fewer surface volcanic activities.