Chapter 2: The Earth

Ch.2:The Earth Sec 1: Planet Earth Our Solar System Planets: M.V.E.M.J.S.U.N. Space Matter: o Asteroids– small, irregularly shaped planet like objects. Found in the asteroid belt in between the orbits of Mars & Jupiter. o Comets– Composed of ice dust particles & frozen gases, look like bright balls of light w/ long feathery tales. o Meteoroids– pieces of space debris- chunks of rock & iron. Usually burned up in Earth’s atmosphere.

Ch.2:The Earth Sec 1: Planet Earth

Getting to Know Earth About 70 % of Earth’s surface is made up of water. Oceans, lakes, rivers, & other bodies of water make up the Earth’s Hydrosphere. 30% of the Earth’s surface is land, this includes continents & islands. This land is known as the Lithosphere. The air we breathe is apart of Earth’s Atmosphere, a layer of gases extending 1,000 miles above Earth’s surface. Our atmosphere is composed of 78% Nitrogen, 21% Oxygen & 1% other gases. The part of Earth that supports life is the Biosphere.

Ch.2:The Earth Sec 2: Forces of Change Earth’s Structure o The Earth is composed of 3 layers. The core (inner & outer), mantle, & the crust. o At the center of the planet is a super hot, solid inner core. 4,000 miles below the Earth’s surface. o Surrounding the inner core is a liquid outer core. This is a liquid band of nickel & iron. This section begins at 1,800 miles below Earth’s surface. o The layer that contains thick, dense rock is know as the Mantle. Consists of silicon, aluminum, iron, magnesium, oxygen & other elements. This mixture continually rises, cools, sinks, warms up, & rises again.

Ch.2:The Earth Sec 2: Forces of Change Inside the Earth

Ch.2:The Earth Sec 2: Forces of Change Plate Movement At one point in time, millions of years ago, the continents of the Earth formed what was known as Pangaea. Over millions of years, this “super-continent” has broken apart into small continents. The theory that the continents were once joined then slowly drifted apart is known as Continental Drift.

Ch.2:The Earth Sec 2: Forces of Change

More about plates... o When the plates spread apart, Magma, molten rock, is pushed up from the mantle & ridges are formed. o Plate Tectonics refers to all these movements which create many of the Earth’s physical features. Majority of the time these movements are gradual at only 4 inches a year (we can’t feel this movement).

Ch.2:The Earth Sec 2: Forces of Change Plates & Plate Movement

Ch.2:The Earth Sec 2: Forces of Change Colliding & Spreading Plates. Subduction- Mountains are created when a sea plate collides with a continental plate.

Ch.2:The Earth Sec 2: Forces of Change o Accretion- pieces of Earth’s crust come together slowly as the sea plate slides under the continental plate.

Ch.2:The Earth Sec 2: Forces of Change Colliding & Spreading Plates...cont. o New land is created when two sea plates converge. This happens when one plates moves under another, forming island chains at the boundary. Sea plates can also pull apart in a process known as Spreading. o The resulting deep crack allows magma from within the Earth to well up between plates. This magma hardens to build undersea volcanic mountains or ridges. This occurs down the middle of the Atlantic Ocean’s floor, pushing Europe and North America away from each other.

Ch.2:The Earth Sec 2: Forces of Change

Folds and Faults Folds: Moving plates sometimes squeeze the Earth’s surface until it folds or bends, in layers of rock. Fault :Plates also grind or slide past each other, this creates cracks in the Earth’s crust. World’s most famous fault is San Andreas Fault, in California.

Ch.2:The Earth Sec 2: Forces of Change

Earthquakes o Earth quakes: Sudden, violent movements of plates along a fault line. Tension builds up along fault lines as the plates stick. The strain eventually becomes so intense that the rocks suddenly snap and shift. This movement releases stored-up energy along the fault. o The Ring Of Fire is one of the most earthquake prone areas on the planet. The cities of Kobe (Japan), San Francisco and Los Angeles are located here. This is a zone of earthquake and volcanic activity surrounding the Pacific Ocean. It marks the boundary where the plates that cradle the Pacific meet the plates that hold the continents surrounding the Pacific.

Ch.2:The Earth Sec 2: Forces of Change o External forces such as wind and water also change the Earth’s surface. Wind and water movements involve 2 processes: Weathering and erosion. o Weathering: The process that breaks down rocks on Earth’s surface into smaller pieces. o Erosion: The wearing away of Earth’s surface by wind, glaciers and moving water.

Ch.2:The Earth Sec 2: Forces of Change Weathering Physical weathering: When large masses of rock are physically broken down into smaller pieces. Ex: water seeps into the cracks of a rock, freezes, then expands, and causes the rock to split. Physical weathering: When large masses of rock are physically broken down into smaller pieces. Ex: water seeps into the cracks of a rock, freezes, then expands, and causes the rock to split. Chemical Weathering: Changes the chemical makeup of a rock. Transforming its minerals or combining them with new elements. Ex: water mixed with Carbon Dioxide from the air easily dissolves certain rocks, such as limestone.

Ch.2:The Earth Sec 2: Forces of Change

Wind and Glacier Erosion o The Chinese Yellow River Basin :is thickly covered with loess, a fertile, yellow-gray soil deposited by the wind. This is a type of wind erosion. o Glaciers can also cause weathering. When glaciers melt and recede, in some places they leave behind large piles of rocks and debris known as Moraines.

Ch.2:The Earth Sec 3: Earth’s Water The Water Cycle o The total amount of water on Earth doesn’t change, however, the Earth’s water is constantly moving– from the oceans to the air, to the ground and finally back to the oceans, this is known as the Water Cycle. o The sun drives the cycle by evaporating water from Earth’s surface. Evaporation is the changing of liquid water into vapor or gas. o When warm air cools, it cannot retain all of its water vapor, so the excess water vapor changes into liquid water, this process is called Condensation. o Tiny droplets of water come together to form clouds. When the clouds gather move water than they can hold, they release moisture, which falls to the Earth as Precipitation– rain, snow, sleet, hail.

Ch.2:The Earth Sec 3: Earth’s Water

Bodies of Salt Water o Oceans– About 97 % of the Earth’s water consists of water that circles the planet, our 4 oceans: the Pacific, Atlantic, Indian, and Arctic. o Seas, Gulfs, & Bays—are bodies of water that are smaller than oceans and are often enclosed by land. o Desalination: The process in which we remove the salt from ocean water and use it as a supply of freshwater, is very expensive, and is still in the early stages of development

Bodies of Freshwater o Only 3% of the Earth’s total water supply is freshwater. 2% of Earth’s total water supply is frozen in glaciers and icecaps. Lakes, rivers, & streams also account for Earth’s small supply of freshwater. o Groundwater– which is freshwater that lies beneath the Earth’s surface, comes from rain & melted snow that filters through the soil & from water that seeps into the ground from rivers & lakes. Wells & springs tap into the groundwater & are important sources of freshwater for people. o Aquifer :An underground porous rock layer often saturated with water in the form of streams Ch.2:The Earth Sec 3: Earth’s Water