Question

theory. it is thought that the earth is about ____ years old and is one of the results of a cosmic ____.

• dust particles collided together to form rocks that became ____ and __ until we had the ____ that we have today.
• early earth was probably ____ due to the __ heat, __ began to settle due to their ____.
• the denser material would ____ to the __ of the planet and the __ material moved towards the ____.

what is the internal structure of earth?

• earth is composed of ____ __, which include the __, __ and ____.
• the core is made up of mostly ____ and some __. the inner core is __, and the outer core is ____.

checkpoint # 1
what is the difference between the inner and outer core?
______
______

Explanation:

These fill-in-the-blank and short-answer questions cover Earth's formation and internal structure, based on basic Earth science principles.

1. For the age of Earth: The widely accepted scientific age is derived from radiometric dating.
2. For planetary formation: Dust particles collided to form planetesimals, then protoplanets, leading to the modern Earth.
3. Early Earth's heat came from accretion and radioactive decay, causing differentiation by density.
4. Earth's internal structure has distinct layers, with the core composed of iron and nickel, differing in state of matter.
5. The core layers differ primarily in their physical state (solid vs. liquid) due to pressure differences.

Answer:

1. First section (Earth formation):

• 4.5 billion
• planetesimals; protoplanets; Earth; planet
• molten; heat from accretion and radioactive decay; materials; density; center; sink; less dense; core

1. Internal Structure of Earth:

• distinct concentric layers; crust, mantle, core
• iron; nickel; solid; liquid

1. Checkpoint #1:

The inner core is a solid sphere composed mainly of iron and nickel, kept solid by the extreme pressure of the overlying layers. The outer core is a liquid layer of iron and nickel, and its churning motion generates Earth's magnetic field.