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Chapter 9: Problem 3

Why are typical rocks found on the Earth's surface much younger than the Earth itself?

Short Answer

Expert verified
Typical rocks found on the Earth's surface are much younger than the Earth itself because of the processes of the rock cycle, weathering and erosion, and plate tectonics. These processes constantly form new rocks, break down old ones, and cause continual recycling of materials, leading to the presence of younger rocks on the Earth's surface.

Step by step solution

01

Understanding the Formation of Rocks

First, understanding how rocks are formed is essential. Rocks are formed in three main ways: sedimentary, igneous, and metamorphic. Sedimentary rocks are formed by the accumulation of sediments. Igneous rocks are formed through the cooling and solidifying of magma or lava. Metamorphic rocks are formed by being subjected to heat and pressure, causing physical or chemical change. These formation ways involve processes that occur over millions of years.
02

Understanding the Rock Cycle

The rock cycle is a model that describes how rocks slowly change from one form to another over time. This cycle is driven by the Earth's internal heat engine, which leads to processes such as precipitation, erosion, sediment transport and deposition, burial and metamorphism, melting, and volcanic eruption. For example, sedimentary rocks can be buried and metamorphosed, metamorphic rocks can melt and solidify to form igneous rocks, igneous rocks can be weathered and eroded to form sediments, and so on. This continuous cycle leads to new rocks formation.
03

Role of Erosion and Weathering

Erosion and weathering play a significant role in making the Earth's surface rocks younger. They constantly break down rocks on the surface into sediment, which is transported and deposited elsewhere, forming new sedimentary rocks. This means older rocks are continuously being replaced by younger ones on the surface.
04

Plate Tectonics

Plate tectonics is the movement of the Earth's lithosphere (the crust and upper mantle). These movements cause rocks to be continually recycled into new rocks, leading to the presence of younger rocks on the Earth's surface. The older rocks typically sink towards the Earth's core due to the subduction zones in plate tectonics.

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Most popular questions from this chapter

Describe the various ways in which the Earth's surface is reshaped over time.

What are the differences among igneous, sedimentary, and metamorphic rocks? What do these rocks tell us about the sites at which they are found?

Identical fossils of the reptile Mesosaurus, which lived 300 million years ago, are found in eastern South America and western Africa and nowhere else in the world. Explain how these fossils provide evidence for the theory of plate tectonics.

On average, the temperature beneath the Earth's crust increases at a rate of \(20^{\circ} \mathrm{C}\) per kilometer. At what depth would water boil? (Assume the surface temperature is \(20^{\circ} \mathrm{C}\) and ignore the effect of the pressure of overlying rock on the boiling point of water.)

The inner core of the Earth is at a higher temperature than the outer core. Why, then, is the inner core solid and the outer core molten instead of the other way around?
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