The GeosphereMiss Napolitano & Mrs. Rodriguez

Environmental Science

The Earth as a System

• The Earth is divided into 4 parts:• Geosphere (rock)• Atmosphere (air)• Hydrosphere (water)• Biosphere (living things)

Discovering the Earth’s interior

• Scientists use seismic waves• Same waves that travel through the Earth

during an earthquake• Altered by that nature of the material through

which it travels• Seismologists measure changes in the speed &

direction of the waves

The Composition of the Earth

• Earth is divided into 3 layers• Crust• Mantle• Core

• Layers get progressively denser towards the center of the Earth

Crust

• Outermost layer

• Solid

• Thinnest layer

• Makes up less than 1% of the Earth’s mass

• 5 km – 8 km think beneath oceans

• 20 km – 70 km thick beneath continents

Mantle

• Rock

• Between the crust & core

• Medium density

• Makes up 64% of the mass of the Earth

Core

• Central part of Earth

• Located below the mantle

• Composed of the densest elements

The Structure of the Earth

• Earth can be divided into 5 layers based on physical properties of the layers• Lithosphere• Asthenosphere• Mesosphere• Outer Core• Inner Core

Lithosphere, Asthenosphere, & Mesosphere

• Lithosphere – solid, outer layer• Crust & upper mantle• Divided into tectonic plates

• Asthenosphere – solid, plastic layer of the mantle• Made of mantle rock that flows & allows

tectonic plates to move

• Mesosphere – lower part of mantle

Outer Core & Inner Core

• Outer core – dense liquid layer

• Inner core – made of mostly iron & nickel• Temperature estimated to be 4,000-5,000°C• Solid because under enormous pressure

• Both the inner core & outer core make up about 1/3 of the Earth’s mass

Earth’s Layers

Plate Tectonics

• Tectonic plates – blocks of lithosphere that glide across the underlying asthenosphere

• Consist of the crust & outermost part of mantle

• Continents are located on plates & move around with them

• Plates may separate, collide, or slip past one another causing mountain formations, earthquakes, or volcanoes

Plate Tectonics

Earthquakes

• Fault – break in the Earth’s crust

• Earthquakes caused when rocks under stress suddenly break along a fault causing ground vibrations

• Many cannot be felt

• Majority take place at or near tectonic plate boundaries• Caused by stresses generated when

plates separate, collide, or slip past each other

Magnitude

• Magnitude – measure of the energy released by an earthquake

• Smallest magnitude that can be felt = 2.0

• Largest magnitude recorded = 9.5

• >7.0 magnitude = widespread damage

• Increase in magnitude by a whole number means 31.7x more energy released than the number below it

Earthquake Hazard

• Earthquakes cannot be predicted, but an area’s earthquake-hazard level can be determined by past & present seismic activity

• Earthquake-resistant buildings are slightly flexible so that they can sway with ground motion• Prevents collapsing

Volcanoes

• Volcano – mountain built from magma (melted rock) that rises from the Earth’s interior

• Located near fault lines where plates are either colliding or separating

• Most volcanoes on land surround the Pacific Ocean in the Ring of Fire

Effects of Volcanoes

• Clouds of hot ash, dust, & gases can flow down a volcano at speeds up to 200 km/hr

• Volcanic ash can mix with water & produce mudflow

• Ash can cause collapsed buildings, buried crops, damaged vehicles, & breathing difficulties

• Major volcanic eruptions can change climate

• Volcanic ash & sulfur can reduce the amount of sunlight that reaches the Earth’s surface, lowering surface temperature

Erosion

• Erosion – materials of the Earth’s surface are loosened, dissolved, or worn away & transported to another place by natural forces (wind, water, ice, gravity)

• Wears down rocks & makes them smoother over time

Wind & Water Erosion

• Water Erosion• Erosion by rivers & oceans• Waves can erode coastlines

• Wind Erosion• Wind can blow soil away quickly in places

where few plants grow• Soft rocks (sandstone) erode more easily

than hard rocks (granite)