the origin of earth

earth forms

Earth formed like the other planets. Different materials in its region of space collided. Eventually the material made a planet. All of the collisions caused Earth to heat up. Rock and metal melted. The molten material separated into layers. Gravity pulled the denser material into the center. The lighter elements rose to the surface (Figure 12.4). Because the material separated, Earths core is made mostly of iron. Earths crust is made mostly of lighter materials. In between the crust and the core is Earths mantle, made of solid rock.

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moon forms

This model for how the Moon formed is the best fit of all of the data scientists have about the Moon. In the early solar system there was a lot of space debris. Asteroids flew around, sometimes striking the planets. An asteroid the size of Mars smashed into Earth. The huge amount of energy from the impact melted most of Earth. The asteroid melted too. Material from both Earth and the asteroid was thrown out into orbit. Over time, this material smashed together to form our Moon. The lunar surface is about 4.5 billion years old. This means that the collision happened about 70 million years after Earth formed.

solar system bodies form

Temperatures and pressures at the center of the cloud were extreme. It was so hot that nuclear fusion reactions began. In these reactions hydrogen fuses to make helium. Extreme amounts of energy are released. Our Sun became a star! Material in the disk surrounding the Sun collided. Small particles collided and became rocks. Rocks collided and became boulders. Eventually planets formed from the material (Figure 12.2). Dwarf plants, comets, and asteroids formed too (Figure 12.3).

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formation earth and moon

Material at a similar distances from the Sun collided together to form each of the planets. Earth grew from material in its part of space. Moons origin was completely different from Earths.

formation the solar system

Our solar system began about 5 billion years ago. The Sun, planets and other solar system objects all formed at about the same time.

the solar nebula

The Sun and planets formed from a giant cloud of gas and dust. This was the solar nebula. The cloud contracted and began to spin. As it contracted, its temperature and pressure increased. The cloud spun faster, and formed into a disk. Scientists think the solar system at that time looked like these disk-shaped objects in the Orion Nebula (Figure

formation of the atmosphere and oceans

An atmosphere is the gases that surround a planet. The early Earth had no atmosphere. Conditions were so hot that gases were not stable.

earths first atmosphere

Earths first atmosphere was different from the current one. The gases came from two sources. Volcanoes spewed gases into the air. Comets carried in ices from outer space. These ices warmed and became gases. Nitrogen, carbon dioxide, hydrogen, and water vapor, or water in gas form, were in the first atmosphere (Figure 12.5). Take a look at the list of gases. Whats missing? The early atmosphere had almost no oxygen.

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the early oceans

Earths atmosphere slowly cooled. Once it was cooler, water vapor could condense. It changed back to its liquid form. Liquid water could fall to Earths surface as rain. Over millions of years water collected to form the oceans. Water began to cycle on Earth as water evaporated from the oceans and returned again as rainfall.

instructional diagrams

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questions

ring of icy debris just beyond Neptune

a. atmosphere

b. nuclear fusion

c. comet

d. solar nebula

e. water vapor

-->  f. Kuiper belt

g. oxygen

Before the Sun formed

-->  a. temperature and pressure was extreme

b. radioactivity began

c. the planets formed

d. all of the above

example of an object in the solar system

a. atmosphere

b. nuclear fusion

-->  c. comet

d. solar nebula

e. water vapor

f. Kuiper belt

g. oxygen

The densest part of planet Earth is the

a. continental crust

b. oceanic crust

-->  c. core

d. mantle

water in the gaseous state

a. atmosphere

b. nuclear fusion

c. comet

d. solar nebula

-->  e. water vapor

f. Kuiper belt

g. oxygen

The Sun formed from

-->  a. a spinning cloud of gas and dust

b. large dense planets pulled to the center by gravity

c. radioactive dust that ignited

d. a collision by two stars

When the solar system first formed

a. life forms were primitive

-->  b. asteroid impacts were common

c. each planets was surrounded by a thick atmosphere

d. all of these

gas missing from Earths early atmosphere

a. atmosphere

b. nuclear fusion

c. comet

d. solar nebula

e. water vapor

f. Kuiper belt

-->  g. oxygen

reaction in which hydrogen atoms change to helium

a. atmosphere

-->  b. nuclear fusion

c. comet

d. solar nebula

e. water vapor

f. Kuiper belt

g. oxygen

Gases in the first atmosphere came from

a. comet impact

b. volcanic outgassing

c. none of these

-->  d. both of these

giant cloud of gas and dust from which the solar system formed

a. atmosphere

b. nuclear fusion

c. comet

-->  d. solar nebula

e. water vapor

f. Kuiper belt

g. oxygen

gases that surround a planet

-->  a. atmosphere

b. nuclear fusion

c. comet

d. solar nebula

e. water vapor

f. Kuiper belt

g. oxygen

The solar system formed from a giant mass of gas and dust.

-->  a. true

b. false

The sun formed billions of years before other objects in the solar system.

a. true

-->  b. false

The solar nebula formed a disk before it formed the sun.

-->  a. true

b. false

The first atmosphere contained nitrogen, carbon dioxide, oxygen, and hydrogen.

a. true

-->  b. false

Objects in our solar system include dwarf planets.

-->  a. true

b. false

All of the stars in the Universe formed at around the same time as our Sun.

a. true

-->  b. false

As Earth formed, gravity pulled lighter materials to the center of the planet.

a. true

-->  b. false

Earths mantle is made entirely of liquid rock.

a. true

-->  b. false

The Sun, planets and other solar system objects formed at about the same time.

-->  a. true

b. false

There was a lot of space debris in the early solar system.

-->  a. true

b. false

Early Earth was much like Earth today.

a. true

-->  b. false

Before there was an ocean, there was water vapor in the atmosphere.

-->  a. true

b. false

Earths moon began as a dwarf planet orbiting the sun.

a. true

-->  b. false

From the time it first formed, Earth has always had an atmosphere.

a. true

-->  b. false

Some of the gases in Earths early atmosphere came from comets.

-->  a. true

b. false

Our solar system began to form about

a. 3 billion years ago.

b. 4 billion years ago.

-->  c. 5 billion years ago.

d. 10 billion years ago.

When the solar nebula contracted and began to spin, it

a. increased in temperature.

b. increased in pressure.

c. formed into a disk.

-->  d. all of the above

The inner planets of our solar system include

a. Pluto.

b. Uranus.

c. Saturn.

-->  d. Mercury.

After the sun formed, material at similar distances from the sun collided to form each of the

a. moons.

-->  b. planets.

c. asteroids.

d. comets.

Earth formed about

-->  a. 4.5 billion years ago.

b. 3 billion years ago.

c. 1 billion years ago.

d. 0.5 billion years ago.

Gases in Earths early atmosphere included

a. oxygen.

b. water vapor.

c. carbon dioxide.

-->  d. all of the above

After the oceans formed on Earths surface, the

-->  a. water cycle began.

b. atmosphere formed.

c. mantle started to cool.

d. all of the above

diagram questions

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