GeologyThe study of Earth

We divide geology into two categories:Physical Geology: To understand Earth’s long history. To understand the changes it has undergoneHistorical Geology: To establish a timeline of the vast number of physical and biological changes that have occurred in the past and may occur in the future

The Formation of Our Galaxy It is believed that our solar system

formed 4.56 billion years ago.

That is 4,560,000,000 years ago.

It all started with the remnants of a defunct or dead star.

Formation (continued) The star exploded and there was a

tremendous amount of dust and small particles floating around. Called a solar nebula

The particles and dust began to spin.

The heavier particles stayed closer to the center than the gaseous particles.

Particles Collide As the particles rotated around a center area,

they banged into each other. These central particles formed billions of small

“planetesimals”. These were about 1 km in diameter.

Gravity began to pull the heavier particles toward the middle

The Sun Ignited!!!!

What Happened Then? When the sun ignited, it began a

process called fusion. This is where hydrogen gets pushed together and form a new material helium. It also releases a tremendous amount of energy.

The energy pushed the gas particles far away, while the heavier planetesimals were not as affected.

Over Millions of Years The solid planetesimals collided to make

bigger bodies (Earth and Venus) The gaseous area collided together to

form some of the larger outer planets.

What about Earth?- Earth was a mix of radioactive

elements, iron, nickel and assorted others. It was getting bombarded by other smaller particles and was expanding quickly.

- The heat from the collisions and the radioactive decay caused some melting in the interior of the Earth

The Layers of Earth- This heat allowed some of the materials to

melt and the denser ones would move to the center.

- The less dense materials would “float” to the top.

- This sinking and floating is still occurring today.

- The center of our Earth is very hot with much molten iron and nickel.

Atmosphere and Oceans- Trapped gaseous materials are allowed

to escape the core today and they still do through volcanic eruptions.

- These eruptions that have occurred, much more frequently earlier, have pushed out enough gaseous materials to form our atmosphere.

- Because we have an atmosphere that condenses, we have water, and oceans.

HomeworkComplete questions 1-7 on page 5

Also complete the key concepts and vocabulary for the first 3 sections of Chapter 1.