WHAT IS THE EARTH?

The Earth's Spheres•The Earth's spheres interact with each other. You could think of each sphere as a different highway in the same area. Cars on the highway can travel independently of one another. But at interchanges, there is an intricate dance between cars traveling on a highway and those entering or exiting it.

The Geosphere•The Earth's geosphere consists of the crust, mantle and the core

•The earth's crust is a relatively thin layer of cool rock that forms the outer skin of the Earth, both dry land and in the ocean

•Below the crust is the mantle, a layer of very hot but mostly solid rock

•The core is beneath the lower mantle. The outer core is molten metals such as iron and nickel that are almost as hot as the surface of the sun. The inner core is a dense ball of solid metal.

•The lithosphere is part of the geosphere. It is the hard rock on and just below the Earth's surface.

Plate Tectonics•As the molten metals in the earth's core churn they drag along plates called tectonic plates. These plates move 2-15 cm per year. This movement influenced the earth’s climate and life's evolution as the continents have combined, separated and recombined.

•These collisions and separations of plates result in landforms such as mountains, islands and continents.

Types of Plate Boundaries•Divergent Plate Boundaries: magma surges upwards and pushes plates apart creating new crust as it cools.

•Transform Plate Boundaries: When two plates meet, they may slip and grind alongside one another, forming a transform plate boundary. The friction between plates at these boundaries often spawn earthquakes

•Convergent Plate Boundaries: When plates collide one of two things will happen. First, one plate may slide beneath another in a process called subduction. The sub ducted crust is heated as it dives into the mantle, and it may send up magma that erupts through the surface in volcanoes. Alternately, the two plates may collide, slowly lifting material from both plates in a process called mountain building.

The Biosphere and Atmosphere• Earth's biosphere and

atmosphere are the living Earth and the ocean of gases that support and protect it

• The Biosphere: the part of the earth which living things interact with nonliving things in Earth's biosphere

• The Atmosphere: When you look at the photo of Earth from space, the atmosphere looks like a very thin blue line. The atmosphere contains the gases, such as oxygen, that organisms use for their life processes. It also contains ozone, a gas made up of oxygen molecules that each have three oxygen atoms. A layer of ozone protects the biosphere from the sun's radiation. The atmosphere also contains other gases such as carbon monoxide and methane these are called greenhouse gases. These keep the earth warm. Humans are adding more gases then necessary to the keep Earth warm.

The Hydrosphere•Water cycles through the lithosphere, biosphere, and atmosphere endlessly

Vocabulary

•Soil: a complex plant-supporting system made up of disintegrated rock, remains, and wastes of organisms, water, gases, nutrients and microorganisms

•Parent Material: the base geological material in a particular location. It can be lava or volcanic ash; rock or sediment deposited by glaciers; sand dunes; sediment deposited by rivers, in lakes, or in the ocean; or bedrock

•Bedrock: the continuous mass of solid rock that makes up the Earth’s crust.

•Soil Horizon/Soil Profile: A cross-section of all the soil horizons in a specific soil

Vocabulary

•Clay: consists of particles less than 0.002mm in diameter

•Silt: consists of particles 0.002 to 0.05mm in diameter

•Sand: consists of particles 0.05 to 2mm in diameter

•Loam: soil with a relatively even mixture of the three particle sizes

Soil Formation

o Weathering: the physical and chemical process that break down rocks and minerals into smaller particles. Physical weathering is mainly caused by wind and rain. Chemical weathering is the process when anything else breaks down parent material or rocks.

o Deposition: the drop off of eroded material at a new location.

o Decomposition: As plants, animals and microorganisms deposit waste or die and decompose, nutrients are incorporated into the soil. Partially decomposed organic matter is known as humus, a dark, spongy, crumbly mass of material made up of complex organic compounds.

Soil Horizons

•Topsoil: A crucial horizon for agriculture and ecosystems in the A horizon or topsoil. Topsoil is the horizon that has the most nutrients

•Lower Horizons: Generally as you move downward through the soil profile, the particles size increases and the concentration of organic mater decreases

Soil Characteristicso Colour: Dark soil is usually rich in humus and

therefore nutrients, whereas pale soil often has less humus and nutrients.

o Texture: Soil texture is based on particle size from clay, silt, and sand. Soil texture influences a soils workability – essentially how easy it is to plant in and harvest from. Soil texture also indicates how porous a soil is, the smaller the size of particles the smaller the spaces between the particles.

o Structure: describes the arrangement of soil particles. You can see this in the clumpiness of soil. Clumpy soil may have a great deal of humus

o pH: Soil acidity or alkalinity affects its ability to support plant growth. Different plants require different pH levels.

Feedback Loops•Negative Feedback Loop – the output of a system moving in one direction acts as input that causes the system to move in the other direction. Input and output respond to each other’s effects, canceling them out and stabilizing the system. A thermostat, for example, stabilizes a room’s temperature by turning the furnace on when the room gets cold and shutting it off when the room gets hot.

•Positive Feedback Loop – have the opposite effect of negative feedback loops. Rather than stabilizing a system they drive it towards an extreme. Erosion, the removal of soil by water, wind, ice, or gravity can lead to a positive feedback loop. Once plants have been cleared from an area and soil is exposed, erosion may increase if the effects of water or wind surpass the rate of plant regrowth. Because positive feedback destabilizes a system and drives it towards an extreme, they rarely happen in natural environmental systems, but are common in systems changed by people