The Earth Contents

1. Structure

Conclusion

The Earth consists of an outer crust (the lithosphere), an underlying solid mantle, and a hot liquid core. Each of these three sets of layers has distinct characteristics. Seismic monitoring has generated insights into the nature of the mantle and the core. The crust is more easily accessible by direct field observation. It's main constituents are oxygen, silicon, iron and aluminium. Calcium, magnesium, potassium and sodium occur in smaller amounts, and other elements, including many familiar metals and materials on which industrial civilisations depend, together comprise less than 2%.

Questions and answers

1.What are the main layers of the Earth's internal structure?

question 1 answers

2.What are the characteristics of the two types of seismic waves generated by earthquakes?

question 2 answers

3.What are the main constituents of the core and the mantle?

question 3 answers

4.Why is the Earth's crust crucial for civilisation?

question 4 answers

5.Describe how the differences between the core, mantle and crust arose.

question 5 answers

6.Why does the lithosphere have a more varied composition than the mantle or the core?

question 6 answers

7.What are the three main rock types and how are they formed?

question 7 answers

8.What elements make up the majority of the Earth's crust?

question 8 answers

9.Give the chemical abbreviations for zinc, potassium, copper, platinum and tungsten.

question 9 answers

Question 1 answer

The lithosphere (or crust) is a thin veneer of soil, sand, gravel and bedrock, which is in contact with the atmosphere and the hydrosphere. Below this lies the mantle; this is divided into an inner region which consists of oxides of magnesium and silicon, and an outer region of iron and magnesium silicates. The core lies underneath the mantle, and at least part of this is liquid.

Question 2 answer

Compressional Waves' - move back and forth in the direction of travel; they can pass through liquid. 'Shear Waves' - move at right angles to the direction of travel; they cannot pass through liquid.

Question 3 answer

The main constituents of the core and mantle are oxygen, iron, silicon and magnesium, which is believed to be similar to that of meteorites.

Question 4 answer

It is a vital source of virtually all the metals, non-metallic minerals, rocks and fuels upon which civilisations now depend.

Question 5 answer

Melting created the difference between the core, mantle and crust. It allowed the material comprising the early Earth to segregate. The very dense liquid iron sank to the centre of the Earth and on top of this floated the residual, relatively light scum of silicon and non-ferrous metals (calcium, magnesium, sodium, potassium and aluminium).

Question 6 answer

Unlike the core and mantle, the lithosphere is exposed to the hydrosphere and atmosphere. Interactions with air and water can chemically alter existing rocks and partially or wholly separate their individual components, to produce a range of different sedimentary rocks, sediments and soils at the surface of the lithosphere.

Question 7 answer

Igneous rocks, metamorphic rocks and sedimentary rocks. Igneous rocks constitute 95% of the crustal mass and are the product of melting. Metamorphic rocks, formed from heating rocks at depth, under high pressures, allowing the separation and remobilisation of rock components. Further melting leads to igneous rock formation. Sedimentary rocks are produced from partial or whole separation of individual rock components.

Question 8 answer

The crust is very heterogeneous. . Oxygen (O) makes up nearly half the crust, almost all of which is combined with silicon (Si) in different proportions to form silicate rocks. Silicon, iron (Fe) and aluminium (Al) together make up a further 40% of the crust. Continental crust bulk composition approximates to that of granite. By contrast oceanic crust is of basaltic composition.

Question 9 answer

Zinc (Zn), Potassium (K), Copper (Cu), Platinum (Pt) and Tungsten (W).