Earth's Early History Review

Hydrogen and Helium are the two lightest elements in the periodic table of elements. What fraction of mass in the in the known universe is made up of Hydrogen and Helium

• 98%
• 100%
• 1%
• 50%
• 2%

A flat, rotating disk of gas and dust surrounding a condensed mass, such as a young stellar object or a forming planet

• Terrestrial planet
• Forst line
• Planetismals
• Accretion Disk

A large cloud of dust and gas in space

• Nebula
• Protostar
• Planetismal
• Jovian Planet

A gas giant planet, examples of which: in our solar system include Saturn, Neptune, and Jupiter

• Jovian Planets
• Terresital Planets
• Nebulas
• Protoplanets

Period of solar system formation during which planetesimals collided with other objects

• gravitational collapse
• heavy bombardment
• planetary accretion
• protostar formation

The boundary in the solar nebula within which compounds such as water and ammonia can form

• frost line
• asteroid belt
• keiper belt
• jovian belt

The contraction of an astronomical object due to the influence of its own gravity

• planetary accretion
• gravitational collapse
• black hole formation
• protostar formation

Because so little can be found of the first rocks to form on Earth, the best evidence for the early formation of our planet comes from studying which of the following?

• Asteroids, lunar rocks, and other objects in the solar system
• Weathering and erosion patterns in extreme enviorments
• The formation of gaseous elements through fusion in our sun
• Fluctuations in chemical compositions of successive lava flows

Mercury, Mars, and Earth’s moon all show evidence of heavy cratering from meteor impacts while Earth shows much less evidence of meteor impacts. The most reasonable conclusion to make from this data is that the early solar system had a much higher density of rocky material, but–

• The Earth's surface has undergone erosion and other ongoing processes
• The rocky material was less likely to reach Earth
• Earth formed much later, when the solar system had fewer meteors
• The protection from impact provided by Earth's atmosphere is decreasing

Why are lunar rocks often a better source of data on the early formation of Earth than rocks found on Earth itself?

• The age of the moon, which, like Earth, is the same as the rest of the solar system
• The lack of active volcanoes, tectonics, and erosional agents on the moon
• The gravitational attraction between Earth and the moon that holds them together
• The absence on the moon of a protective atmosphere to shield it from impacts