The Dynamic Earth Unit 3

3-1 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 divided this system into four parts: -The Geosphere (rock) -The Atmosphere (air) -The Hydrosphere (water) -The Biosphere (living things)

The Earth as a System

The Geosphere -Extends from the core to the crust. -Mostly solid, rocky part of the Earth. -Extends from the core to the crust. -The atmosphere is a mixture of gases that makes up the air we breathe. -Gases are found in the first 30 km above the Earth’s surface.

The Hydrosphere -Made up of all the water on or near the Earth’s surface. -Oceans cover nearly three- quarters of the globe. -Water is also found in the atmosphere, on land, and in the soil.

The Biosphere -Part of the Earth where life exists. -Thin layer that extends from about 9 km above the Earth’s surface to the bottom of the ocean. -Made up of parts of the geosphere, atmosphere, and hydrosphere

Discovering Earth’s Interior -Seismic waves are used to learn about Earth’s interior. -Seismic waves travel through Earth’s interior during an earthquake. -The speed and direction of seismic waves reveal the different layers of the Earth.

The Composition of the Earth -The Earth is divided into three layers: The crust The mantle The core -These layers are made up of progressively denser material toward the center of the Earth.

The Crust -Makes up less than 1 percent of the planet’s mass. -Thin, solid outermost layer of the Earth. -Makes up less than 1 percent of the planet’s mass. -Is 5 km to 8 km thick beneath the oceans and 20- 70 km thick beneath the continents.

The Mantle Layer of molten rock between the Earth’s crust and core. -Makes up 64 percent of the mass of the Earth.

The Core -Central part of the Earth below the mantle. -Composed of nickel and iron. -Estimated temperature: btw 4,000°C to 5,000°C - it is solid because of enormous pressure.

Earth’s Structure Earth can be divided into five layers based on physical properties: -Lithosphere: solid, outer layer of the crust and rigid upper part of the mantle. -Is divided into huge pieces called tectonic plates.

Earth’s Structure (cont’d) -Asthenosphere: solid, plastic layer of the mantle beneath the lithosphere. -Made of slowly flowing mantle rock, which allows tectonic plates to move on top of it. -Mesosphere: lower part of the mantle

Plate Tectonics Divisions of lithosphere. Glide across the asthenosphere. Major plates: Pacific, North America, South America, Africa, Eurasian and Antarctic.

Plate Boundaries Site of major geologic activity. Plates may collide, pull apart, or “slip” past one another. Forces may result in earthquakes, volcanoes or mountain building.

Earthquakes Faults are breaks in the crust. Slippage along faults vibrate crust create earthquakes. Richter scale quantifies magnitude earthquake energy. -smallest magnitude: 2.0 -largest magnitude: 9.5 Most active fault in N.A.: San Andreas along California.

Where do Earthquakes Occur?

FYI: Earthquake Hazard Scientists cannot predicts when earthquakes will take place. However, they can help provide information about where earthquakes are likely to occur helping people prepare. An area’s earthquake-hazard level is determined by past and present seismic activity. Earthquake-resistant buildings, built in high risk areas, are slightly flexible so that they can sway with the ground motion preventing them from collapsing.

Plate Tectonics and Mountain Building -Colliding plates form mountain ranges Ex. The Himalaya Mountains

Volcanoes Mountain built from magma. Can occur on land or in the sea. Often located near tectonic plate boundaries- plates are either colliding or separating from one another. Majority of active volcanoes on land are located along tectonic plate surrounding the Pacific Ocean.

Volcanoes: The Ring of Fire

Local Effects of Volcanic Eruptions -Clouds of ash, dust, and gases can flow down the slope of a volcano at speeds of up to 200 km/hr. -Can burn everything in its path. -Volcanic ash mixed with water can produce mudflows. -Falling ash can cause buildings to collapse under its weight, bury crops, damage the engines of vehicles, and cause breathing difficulties.

Global Effects of Volcanic Eruptions -Major eruptions can change Earth’s climate for several years. -Clouds of volcanic ash and sulfur rich gases may reduce the amount of sunlight that reaches the Earth’s surface. -Reduction in sunlight can cause a drop in the average global surface temperature.

Erosion -Process in Earth’s surface is loosened, dissolved, or worn away and transported by wind, water, ice or gravity. -Wears down rocks and makes them smoother with time (reason why older mountains are smoother than younger ones).

Water Erosion -Waves from ocean storms can erode coastlines. -Rivers and oceans can produce major changes on Earth’s surface. -Waves from ocean storms can erode coastlines. -Rivers can carve deep gorges into the landscape.

Wind Erosion -At beaches and in deserts, wind can blow soil away quickly. -Soft rocks, such as sandstone, erode more easily than hard rocks, such as granite do.

Sect 2: The Atmosphere Mixture of gases: Nitrogen (N₂)- 78% Oxygen (O₂)- 21% CO₂, H₂O, argon- 1% Insulates the earth from heat and cold. Held in place by gravity

Layers of the Atmosphere Troposphere: closest to surface, site of weather. Stratosphere: above the troposphere, site of ozone -ozone (O₃) protects against harmful UV radiation from sun. Mesosphere: coldest layer. Thermosphere: lowest layer is ionosphere- site of aurora borealis

Energy in The Atmosphere Energy from the sun is transferred as heat by: Radiation: across space. Conduction: warm to cold. Convection: air molecules -hot air rises, cold air sinks.

The Greenhouse Effect Process in which gases trap heat near the Earth’s surface. -sunlight heats the surface the day. -some of the heat escapes back into space. -remainder of heat is trapped by greenhouse gases (methane, CO₂, nitrous oxide, water vapor).

Sect 3: The Hydrosphere and Biosphere Hydrosphere: includes all water on or near Earth’s surface… -oceans, lakes, icecaps, soil, clouds.

The Water Cycle Continuous movement of water between air and land. 3 major processes: -evaporation: liquid to vapor. -condensation: vapor to drop- lets, forms clouds. -precipitation: rain, snow, sleet, hail.

Oceans Single, interconnected body of water. Covers 70% of planet. Largest ocean: Pacific -deepest point: Challenger Deep -currents move clockwise north of equator; counterclockwise south of the equator.

Oceans (cont’d) 2nd largest ocean: Atlantic Smallest ocean: Arctic -unique feature: pack ice covers much of ocean’s surface.

Ocean Water Contains dissolved salts, most of which is sodium chloride. Salinity: concentration of all salts in water. -lower where fresh water flows into ocean. -higher where water evaporates quickly.

Ocean Zones Surface zone: warm top layer; currents mix warm and cool water. Thermocline: boundary between warm and cold water; temperature drops faster with depth than other zones. Deep zone: bottom zone with coldest temperatures.

Ocean Currents Surface: wind driven, result from global winds. -may be warm or cold. -can flow for hundreds of km.s ex. Gulfstream -influence climate of land. Deep: flow slowly on ocean floor. -cold polar water sinks, moves toward the equator.

Global Temperature Regulator Ocean waters absorb, store energy from sunlight. Water absorbs, releases heat more slowly than land, results in slower atmospheric temperature changes. Temperature regulation prevents extremes on Earth.

Fresh Water Contains insignificant amounts of salts. ≈ 3% of all water. Most is locked up in icecaps, glaciers Liquid form is found in lakes, rivers, wetlands, the soil, atmosphere.

River Systems Network of streams that drains an area of land. Contains all of the land drained by a river, including the main river and its tributaries: small streams that empty into a river. Mississippi River system covers ≈ 40% of the contiguous U.S.

Groundwater Area underground that collects rain, melting snow. Less than 1% of all water. Fulfills the human need for fresh drinking water, supplies agricultural and industrial needs. Aquifers: rock layer that stores and allows the for the flow of groundwater. -recharge zone: surface of land where water enters aquifer.

The Biosphere Narrow layer of planet where life is found (includes geosphere, lower atmosphere, hydrosphere). Closest to surface because of ample sunlight there. Dependent on gravity, water, nutrients.

Energy Flow Through the Biosphere Begins as sunlight trapped by plants in photosynthesis. Dead organisms are broken down, its energy and nutrients are passed on to others. Recycling of nutrients and energy flow make life possible.

Mount St. Helens, Washington State

Mount St. Helens, Washington State