Earth Science: Layers of the Earth

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Questions and Answers

What is the primary composition of the outer core?

Liquid iron-nickel alloy (correct)

Solid iron and nickel

Magnesium oxide

Silicate minerals

What happens to S-waves at the Gutenberg Discontinuity?

They transform into P-waves

They cannot travel through the region (correct)

They become absorbed completely

They speed up significantly

Which layer of the Earth is characterized by a solid composition and high density?

Outer core

Mantle

Inner core (correct)

Crust

Who discovered the Mohorovicic Discontinuity and when?

Andrija Mohorovicic in 1909 Signup and view all the answers

What is the average depth of the Mohorovicic Discontinuity under the continental crust?

32 km Signup and view all the answers

What defines the boundary separating the outer core and inner core?

Lehmann Discontinuity Signup and view all the answers

Which layer of the Earth is primarily composed of silicate materials?

Mantle Signup and view all the answers

What layer of the Earth is solid yet located in a liquid environment?

Inner core Signup and view all the answers

What characterizes the oceanic crust compared to the continental crust?

It is primarily made of basalts and is denser than continental crust. Signup and view all the answers

Which statement accurately describes the lithosphere?

It includes both the crust and the uppermost part of the mantle. Signup and view all the answers

What distinguishes the upper mantle from the lower mantle?

The upper mantle includes the lithosphere while the lower mantle is less ductile. Signup and view all the answers

Which of the following accurately describes the core of the Earth?

The outer core is liquid, while the inner core is solid and hotter. Signup and view all the answers

How thick is the mantle compared to the Earth’s total mass?

It contributes about 67% of the total mass. Signup and view all the answers

What mineral compositions does 'sima' represent in the oceanic crust?

Silicate and magnesium. Signup and view all the answers

In which part of the mantle are rocks considered to be partially molten?

The upper mantle, specifically in the asthenosphere. Signup and view all the answers

Which statement about the oceanic and continental crust is incorrect?

Continental crust exists beneath the ocean floor. Signup and view all the answers

Study Notes

Earth's Structure

Earth consists of three major layers: Crust, Mantle, and Core.

Crust

Outermost layer made of solid rocks and minerals.
Two classifications:
- Oceanic Crust
  - Extends 5 to 10 kilometers beneath the ocean floor.
  - Composed of basalts; referred to as “sima” (silicate and magnesium).
  - Dense and thin, formed at mid-ocean ridges.
- Continental Crust
  - Composed mainly of granites, called “sial” (silicate and aluminum).
  - Thickness can be over 70 kilometers; lighter than oceanic crust.

Mantle

Lies beneath the crust, comprised of solid rock.
Extends to a depth of about 2900 kilometers, contributing to 67% of Earth's total mass.
Temperature and pressure increase with depth; heat transfer from the core raises temperatures.
Divided into two layers:
- Upper Mantle
  - Extends from the crust to about 410 kilometers.
  - Mostly solid but malleable areas contribute to tectonic activity; includes the lithosphere (outer solid part).
- Lower Mantle
  - Extends from about 660 to 2700 kilometers deep.
  - Hotter and denser than the upper mantle; includes the asthenosphere (semi-molten layer).
  - Mesosphere is the lowest part, adjacent to the outer core.

Core

Extremely hot and dense, located about 2900 kilometers below the surface.
Composed of two parts:
- Outer Core
  - Liquid iron-nickel alloy; temperature ranges from 4000 to 5000 degrees Celsius.
  - Responsible for generating Earth’s magnetic field.
- Inner Core
  - Composed mainly of dense iron and nickel; not affected by high temperature due to its pressure.

Layer Division

Chemical division based on composition: Crust, Mantle, Core.
Mechanical division based on temperature and phase: Lithosphere, Asthenosphere, Outer Core, Inner Core.

Discontinuities

Mohorovicic Discontinuity (Moho)
- Boundary between crust and mantle; average depth of 8 km under oceans and 32 km under continents.
Gutenberg Discontinuity
- Boundary where P-waves slow down, indicating the presence of molten materials in the outer core.
Lehmann Discontinuity
- Boundary between inner and outer core; supports the understanding of a solid inner core and liquid outer core based on seismic wave analysis.

Thickness Measurements

Crust: Average thickness of 32 km.
Mantle: Approximately 2853 kilometers thick.
Core: Outer Core around 2270 kilometers; Inner Core about 1216 kilometers thick.

Tectonic Plates

Massive slabs of solid rock that form Earth's outer shell, responsible for geological activities such as earthquakes and volcanic eruptions.

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Description

Explore the Earth's interior through this quiz focused on its three major layers: the crust, mantle, and core. Delve into the characteristics and classifications of the crust, including oceanic and continental types. Test your knowledge of geological terms and concepts!