ELS | Lesson 2

• What does Earth science study?

  Earth science studies the entire planet as a system of interacting parts called subsystems.
• What is the focus of Earth science?


  It focuses on the processes and changes within and among the subsystems.
• How are the subsystems of Earth related to each other?

  Each subsystem can be studied separately, but they are ultimately dependent on and connected with the other subsystems.
• What are the four subsystems of Earth?

  • Geosphere
  • Hydrosphere
  • Atmosphere
  • Biosphere
• What does the geosphere refer to?

  The geosphere refers to the solid Earth.
• What is the composition of the geosphere?

  It is composed of naturally-occurring solid aggregates of minerals, organic material, or natural glass called rocks, and loose particles of rocks called regolith.
• What are the three layers of the geosphere?

  1. Crust
  2. Mantle
  3. Core
• What is the thickness range of the Earth's crust under oceans?

  The thickness of the Earth's crust under oceans is about 5 kilometers or 3 miles.
• What is the thickness range of the Earth's crust under continents?

  The thickness of the Earth's crust under continents can be up to 70 kilometers or 43 miles.
• How deep does the mantle extend?

  The mantle extends to a depth of about 2,900 kilometers (1,800 miles).
• What is the composition of the mantle?

  The mantle is composed of silicate rocks rich in iron.
• What are the two parts of the Earth's core?

  The Earth's core consists of a liquid outer core and a solid inner core.
• What is the depth range of the outer core?

  The outer core extends from a depth of about 2,900 kilometers or 1,800 miles to 5,150 kilometers or 3,200 miles.
• What is the composition of the outer core?

  The outer core is composed mainly of iron and nickel.
• What is the depth range of the inner core?

  The inner core extends from a depth of about 5,150 kilometers or 3,200 miles to the center of the Earth at about 6,371 kilometers or 3,959 miles.
• What is the composition of the inner core?

  The inner core is solid and composed mainly of iron and nickel.
• What percentage of Earth's surface is covered by oceans and seas?

  About 71% of Earth's surface is covered by water, primarily in the form of oceans and seas.
• Where is freshwater found on Earth?

  Freshwater is found in rivers, lakes, glaciers, and underground in aquifers.
• What does the biosphere include?

  The biosphere includes all ecosystems and living organisms, interacting with the atmosphere, hydrosphere, and lithosphere.
• What are the layers of Earth's atmosphere?

  • Troposphere
  • Stratosphere
  • Mesosphere
  • Thermosphere
  • Exosphere
• What is the composition of Earth's atmosphere?

  The atmosphere is mainly composed of 78% nitrogen and 21% oxygen, with trace amounts of other gases such as argon, carbon dioxide, and neon.