1. Earth’s Internal Structure

Question 1

What are the three layers of the Earth’s interior according to old views?

Answer 1

The three layers, now considered obsolete, were:
SiAl: Topmost layer, consisting of Silica and Aluminium, with low density.
SiMa: Middle layer, composed of Silica and Magnesium, with higher density.
NiFe: Innermost layer, made up of Nickel and Iron.

Question 2

What characterizes the SiAl layer of the Earth?

Answer 2

The SiAl layer is characterized by its composition of Silica and Aluminium, being the topmost layer with low density, and it floats on the SiMa layer.

Question 3

Describe the SiMa layer’s composition and properties.

Answer 3

The SiMa layer is composed of Silica and Magnesium. It has a higher density compared to the SiAl layer and lies beneath it.

Question 4

What is the NiFe layer, and where is it located?

Answer 4

The NiFe layer is composed of Nickel and Iron and is the innermost layer of the Earth.

Question 5

How is the Earth’s interior structured according to recent views?

Answer 5

The Earth’s interior is structured similarly to an onion, divided into Crust, Mantle, and Core.

Question 6

What is the average density of the Earth’s crust and how does it compare to the overall density of the Earth?

Answer 6

The average density of the Earth’s crust is 2.7 g/cm³, which is less than half of the Earth’s overall density of 5.51 g/cm³.

Question 7

How does temperature change with depth in the Earth’s crust?

Answer 7

The temperature in the Earth’s crust increases by approximately 30°C for every kilometer you go deeper.

Question 8

What are the main differences between continental and oceanic crust?

Answer 8

Continental crust is thicker, averaging 35 km and up to 100 km in places like the Himalayas, and composed mainly of granite, which is lighter and less dense. Oceanic crust is thinner, with an average depth of 5 km, and is composed of denser basaltic rocks.

Question 9

What types of rocks are found in the continental crust and what are their characteristics?

Answer 9

The continental crust is composed of granite rocks on the surface and gabbro rocks in the interior portions that touch the mantle. Andesite rocks can also be found in the topmost layer. These rocks are categorized as felsic due to their composition of feldspar and silica.

Question 10

Describe the composition of the oceanic crust.

Answer 10

The oceanic crust is primarily composed of basaltic rocks, which are denser and heavier. It contains mafic rocks, consisting of magnesium and iron.

Question 11

What are the most abundant minerals found in the Earth’s crust and their percentages?

Answer 11

The most abundant minerals in the Earth’s crust are:
Oxygen (O) - 46.6%
Silica (Si) - 27.7%
Aluminium (Al) - 8.1%
Iron (Fe) - 5%
Calcium (Ca) - 3.6% Followed by sodium (Na), potassium (K), and magnesium (Mg).

Question 12

What percentage of the Earth’s volume and mass does the crust contribute?

Answer 12

The crust contributes around 0.5-1% to the Earth’s volume and less than 1% of the Earth’s mass.

Question 13

What mnemonic can help remember the sequence of minerals found in the Earth’s crust based on abundance?

Answer 13

The mnemonic OSAIC can help remember the order: Oxygen, Silica, Aluminium, Iron, and Calcium.

Question 14

What is the most abundant mineral found in the entire Earth?

Answer 14

The most abundant mineral in the entire Earth is Iron (Fe), which constitutes about 34.5% of the Earth’s mass.

Question 15

What elements make up the mantle of the Earth?

Answer 15

The mantle consists of elements such as Oxygen (O), Silicon (Si), and Magnesium (Mg), with Oxygen being the most abundant at 45%.

Question 16

What are the lithosphere and asthenosphere, and how do they interact?

Answer 16

The lithosphere includes the brittle upper portion of the mantle and the crust, and it floats over the semi-solid asthenosphere, which is denser and is the location of the ‘magma chamber’ that aids in volcanic eruptions.

Question 17

Describe the characteristics of the asthenosphere.

Answer 17

The asthenosphere is semi-solid, denser than the lithosphere, and contains the ‘magma chamber’. It is also a zone of low seismic wave velocity.

Question 18

How significant is the mantle in terms of Earth’s volume and mass?

Answer 18

The mantle contributes 83% to Earth’s volume and approximately 67% to its total mass.

Question 19

What is the difference between magma and lava?

Answer 19

Magma is molten rock inside the Earth, while lava is molten rock that has erupted onto the Earth’s surface.

Question 20

What kind of nuclear activity occurs in the mantle?

Answer 20

Radioactive elements in the mantle undergo decay, producing heat energy that causes rocks to melt, forming magma.

Question 21

How do seismic waves behave in the mantle?

Answer 21

Seismic waves, specifically primary and secondary waves, slow down when passing through the asthenosphere due to its semi-solid nature.

Question 22

What percentage of Earth’s volume and mass does the core contribute?

Answer 22

The core contributes about 16% to Earth’s volume and approximately 33% to its total mass.

Question 23

Why is the outer core in a liquid state and what elements are found there?

Answer 23

The outer core is in a liquid state due to the high temperatures from primordial heat and radioactive decay, not nuclear fusion. It mainly consists of iron, nickel, and sulfur.

Question 24

How do convective currents in the outer core affect the Earth?

Answer 24

Convective currents in the outer core, driven by temperature differences, contribute to the generation of Earth’s magnetic field.

Question 25

What is primordial heat and how did it affect the early Earth?

Answer 25

Primordial heat is the residual heat from Earth’s formation, which initially caused the planet to be in a gaseous and liquid state. It played a role in the formation of the Earth’s crust and the occurrence of volcanic eruptions.

Question 26

How does temperature change with depth inside the Earth?

Answer 26

Temperature increases with depth inside the Earth, contributing to the different states of matter in the core and affecting geological processes.

Question 27

Describe the inner core’s state, temperature, and density.

Answer 27

The inner core is solid, with temperatures around 6000°C—comparable to the Sun’s surface—and has the maximum density on Earth’s surface, approximately 13 g/cm³.