Answer:
I say, it would really be around like 50-500km. Really, it would be 70km.
Explanation:
Magma rises with convective currents, then cools and spreads intent on form ocean-floor crust. The place to start for melting has lengthy been idea to be at <em>70 kilometers</em> under the seafloor.
Answer: Option (C)
Explanation: The rocks at the continental crust are present since a long time, and the oldest rocks so far encountered from the continental crust is approximately 4.4 billion years old.
This has been determined by the Uranium-Lead dating method (Ur₂₃₈-Pb₂₀₆).
Oceanic rocks are estimated to be of very recent age i.e about only 180 million years old.
Answer:
1. Wind
When strong winds blow, the topsoil along with the organic matter is carried away by the wind. This happens more often when the land is not covered with grass or plants. Such conditions are very common in desert and semi-desert regions where strong winds blow very frequently.
2. Water
When it rains in the hilly areas, the soil gets washed away towards the plains. The running water deposits the mineral-rich soil in the riverbed and over the years this deposition of soil can change the course of the river. This can lead to floods which cause the destruction of life and property. Water erosion leads to loss of agriculture potential.
3. Overgrazing
When cattle are allowed to graze on the same field repeatedly, all the available grass, including the roots are eaten by them. This makes the topsoil vulnerable to wind and flowing water, leading to soil erosion.
4. Deforestation
Humans have taken land from the forest to cultivate in order to feed the ever-increasing population and to build houses, industries, etc. Cutting down of trees on a large scale for these purposes is deforestation. The roots of trees hold the soil together, thus preventing the soil from getting uprooted. When large areas of the forest are cleared, the topsoil gets eroded by wind and flowing water.
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