Chapter 3 Section 1

The Earth as a System  The earth is an integrated system that consists of rock, air, water, and living things that all interact with each other.  Scientists have divided this system into four parts, the geosphere, atmosphere, hydrosphere, and biosphere.

Geosphere  The solid part of the Earth that consists of all rock, and the soils and sediments on Earth’s surface is the geosphere.  Most of the geosphere is located in Earth’s interior.

 The atmosphere is the mixture of gases that makes up the air we breathe.  Nearly all of these gases are found in the first 30 km above the Earth’s surface. Nitrogen78.084% Oxygen20.946% Argon0.934% Carbon dioxide0.038% Water vaporLess than 1% Other0.002% Atmosphere

Hydrosphere  The hydrosphere makes up all of the water on or near the Earth’s surface.  Much of this water is in the oceans, which cover nearly ¾ of the Earth.

Biosphere  The biosphere is made up of parts of the geosphere, atmosphere and the hydrosphere.  The biosphere is the part of the Earth where life exists.

The Composition of the Earth  Scientists divide the Earth into three layers; the crust, mantle, and the core.  The crust is Earth’s thin outer layer and makes up less than 1% of the planet’s mass.  The mantle is the layer beneath the crust and makes up 64% of the Earth’s mass.  The core is the innermost layer and is composed of the densest elements.

The Structure of the Earth  Earth’s outer layer is the lithosphere, which is a cool, rigid layer that is 15 km to 300 km thick.  It includes the crust and uppermost part of the mantle. It is divided into huge pieces called tectonic plates.

Asthenosphere  The asthenosphere is the layer beneath the lithosphere.  The asthenosphere is a plastic, solid layer of the mantle made of rock that flows very slowly and allow tectonic plates to move on top of it.

Plate Tectonics  Tectonic plates glide across the asthenosphere in much the same way as a chunk of ice drifts across a pond.  Continents that are on tectonic plates move along with them.  The major tectonic plates include the Pacific, North American, South American, African, Eurasian, and Antarctic plates.

Plate Boundaries  Plates may separate from one another, collide with one another, or slip past one another.  Enormous force is generated at tectonic plate boundaries, where the crust is pulled apart, is squeezed together, or is constantly slipping.

 The forces produced at the boundaries of tectonic plates can cause mountains to form, earthquakes to shake the crust, and volcanoes to erupt.

Earthquakes  A fault is a break in the Earth’s crust along which blocks of the crust slide relative to one another.  When rocks that are under stress suddenly break along a fault, a series of ground vibrations is set off. These vibrations of the Earth’s crust caused by slippage along a fault are known as earthquakes. Where earthquakes have struck

The Richter Scale  The Richter scale is used by scientists to measure the magnitude, or the amount of energy released by an earthquake.  The smallest magnitude that can be felt is approximately 2.0, and the largest magnitude ever recorded is 9.5. Earthquakes can cause severe damage after 7.0.  Each increase of magnitude by a whole number indicates the release of 31.7 times more energy than the whole number below it.

Volcanoes  A volcano is a mountain built from magma that rises from the Earth’s interior to the surface.  Volcanoes are often located near tectonic plate boundaries. 

Global Effects of Volcanic Eruption  Major volcanic eruptions can change the Earth’s climate for several years.  In large eruptions, clouds of volcanic ash and sulfur-rich gases may reach the upper atmosphere.  As soon as the ash and gases spread across the planet, they can reduce the amount of sunlight that reaches Earth’s surface.

Erosion  The removal and transport of surface material is called erosion.  Wind erosion blows the soil away, which is where the plant’s roots are located.  Water erosion is caused by both rivers and oceans. Waves from ocean storms can erode coastlines, and over time, rivers can carve deep gorges into the landscape.