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Have you ever looked around when you are in nature and wondered how all of its different aspects work together? What type of systems make up Earth? What processes work to recycle the materials on Earth? Where does all the energy needed for these processes come from? Earth’s Systems Interact There are four major systems on Earth: the geosphere, the hydrosphere, the atmosphere, and the biosphere. The geosphere is all of the solid and molten rocks, the soil, and sediments. The outermost All the parts of Earth

work together

portion of the geosphere is called the lithosphere. The hydrosphere is made of all water and ice. Our air makes up the atmosphere, and humans and other living things make up the biosphere. These systems interact in multiple ways to affect Earth’s surface materials and processes. All of Earth’s processes are the result of energy flowing and matter cycling within and among the planet’s systems. This energy is derived from the Sun and Earth’s hot interior. All of Earth’s systems are connected and affect each one another. The Rock Cycle Geologists classify rocks into three categories: sedimentary, igneous, and metamorphic. Rocks are separated into these three types based on how they were made. A rock’s physical characteristics reflect the processes under which it formed, as does a rock’s mineral composition. When rocks undergo additional processes, they can change from one type of rock to another. Depending on the processes, any type of rock can become any of the other types. It could even become a new rock of the same type. For example, a sedimentary rock could become a metamorphic rock, an igneous rock or a new type of sedimentary rock, depending on what happens to it. The processes by which rocks change into new rocks make up the rock cycle. Energy from the Sun and Earth’s hot interior drive the processes in the rock cycle.

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Rocks can be changed through the processes of weathering, erosion and

deposition, and compaction and cementation, as well as changes in

temperature and/or pressure.

Igneous Rocks Igneous rocks are formed when lava or magma cools and solidifies. This solidification is known as crystallization. Lava and magma are both molten rock. Molten rock under Earth’s surface is called magma. When magma erupts out of a volcano, or seeps through cracks in Earth’s crust, it is called lava. Igneous rocks have interlocking mineral crystals. These crystals vary in size, depending upon how rapidly they cooled. When magma cools under Earth’s surface, it solidifies very slowly because the temperature is so much higher in Earth’s interior. This gives mineral crystals a long time to grow and become quite large. Igneous rocks that cool slowly under Earth’s surface are known as intrusive igneous rocks. To remember this concept, think of “internal” when considering intrusive igneous rocks. Intrusive igneous rocks form in Earth’s interior. It is much cooler on Earth’s surface than it is below. When lava cools on Earth’s surface, it solidifies very quickly. This does not give mineral crystals very much time to grow, so they will be quite small. Sometimes, they will cool so quickly that no crystals will form at all. In that case, the rock will have the characteristics of glass. A volcano may shoot blobs of lava into the air. These blobs can cool so quickly that they solidify before they even hit the ground. Igneous rocks that cool quickly on or above Earth’s surface are known as extrusive igneous rocks. To remember this concept, think of “external” when considering extrusive igneous rocks. Extrusive igneous rocks form on Earth’s exterior). As part of the rock cycle, old igneous rocks can form new igneous rocks. How do you think this can happen? (Recall that igneous rocks form when molten rock, magma or lava, solidifies.) Sedimentary Rocks Rocks can be broken down by forces on Earth in a process called weathering. Once rocks are broken down, the smaller pieces are called sediments. Sediments can be carried from place to place. This process is called erosion. Erosion carries sediments through wind, water, gravity or other means. For example, sediments can travel downstream in a river. They can also roll downhill in a landslide. Eventually, sediments stop moving and settle into layers. This process is called deposition.

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Layers of sediment can be crushed together as more sediment gathers on top. This crushing is called compaction. Sometimes, water will fill in the tight spaces between the grains of sediment. Eventually, the water evaporates. When this happens, any minerals that were dissolved in the water are left behind. Small mineral crystals grow while the water evaporates. These crystals “glue” the sediment grains together in a process called cementation. Once the sediment grains are bound together, they become a sedimentary rock. Metamorphic Rocks When rocks are buried deep in Earth’s crust, heat and pressure can cause the buried rocks to be altered to form new rocks. These are called metamorphic rocks. Metamorphic rocks are often characterized by bands or wavy layers of mineral crystals or by the presence of unusual minerals.

These hills are made of layers of sedimentary rock called sandstone.

These layers of sandy sediment were deposited one on top of

another before they were compacted and cemented together.

Pressure can change an existing rock into a new metamorphic rock by changing the rock’s texture. Sometimes the sediment grains of a sedimentary rock or the crystals of an igneous or other metamorphic rock will be squeezed tightly together. This can change the rocks into new, denser metamorphic rocks. Many sedimentary rocks already contain parallel layers. These parallel layers can be squeezed by pressure and become the wavy layers of a metamorphic rock. Pressure can also change an existing rock into a new metamorphic rock by changing the rock’s mineral composition. A mineral is defined by the elements of which it is made and by its crystal structure. The crystal structure is the internal arrangement of the atoms that make up the crystal. Sometimes the pressure is great enough that it will change the internal arrangement of atoms by crushing the atoms together. Because this changes the crystal structure, it changes the minerals and the mineral composition, which in turn changes the rock into a new metamorphic rock. Heat can also change an existing rock into a new metamorphic rock by changing the rock’s mineral composition. Heat can also cause water or other chemicals to evaporate out of certain minerals. These chemical reactions change the mineral composition of the existing rock and a new metamorphic rock with a different mineral composition is formed. When heat changes an existing rock into a new metamorphic rock, the rock may become soft, but, the rock will still be in solid form. Suppose the heat is great enough to actually melt the rock into liquid form. When the rock solidifies again, it will become an igneous rock, not a metamorphic rock. Heat that changes rocks into metamorphic rocks is like candle wax. A little bit of heat will make the wax soft enough for you to mold it into a new shape.

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Carbon And Oxygen Cycles In living systems, plants absorb carbon dioxide gas during photosynthesis and use the carbon to produce other carbon-containing molecules, such as sugars and starches. Consumers eat these producers and breakdown these molecules to obtain energy through respiration. Carbon dioxide gas is released during respiration. Decomposers also break down molecules via respiration. Oxygen also cycles through living systems. Producers release oxygen during photosynthesis, and most organisms, including most plants and animals, take in oxygen and use it during respiration. Another source of carbon that enters an ecosystem is through the release of carbon dioxide and carbon monoxide from burning fossil fuels and vehicle exhaust.

The carbon-oxygen cycle is vital to life on Earth.

Nitrogen Cycle Nitrogen moves from the air to the soil, into living things, and back into the air. Free nitrogen in the atmosphere combines with other elements through nitrogen fixation. This process occurs due to nitrogen-fixing bacteria. Nitrogen is fixed into compounds used by other organisms. For example, consumers eat nitrogen compounds in plants to build proteins and other substances. Decomposers break down waste and the remains of organisms and return nitrogen compounds to the soil. Certain bacteria release some free nitrogen back into the air.

Biomass is organic material from plants and animals. When living organisms die, bacteria and other decomposers break down the materials (breaking larger molecules into smaller ones) in the biomass. The decay of biomass also releases energy stored in the chemical compounds in biomass.

The Source Remember that the energy that drives the carbon, oxygen, and nitrogen cycles comes from the Sun. The Sun also helps to power interactions among Earth’s hydrosphere, biosphere, geosphere, and atmosphere.

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Match the terms below with the best description.

1. Igneous rock The air

2. Biosphere Bacteria are required to complete

3. Atmosphere Formed from lava and magma

4. Sedimentary rock All rocks and soil

5. Carbon cycle All living things

6. Metamorphic rock Includes photosynthesis and respiration

7. Geosphere Water and ice

8. Nitrogen cycle Forms by compaction and cementation

9. Hydrosphere Forms from heat and pressure

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Importance Of Soil Quality In Agriculture Although children are probably familiar with dirt from an early age, they may not be aware that it can have different levels of quality. That quality is important for determining how well the soil supports plant growth. Take a trip with your child to the local home improvement store or to a store with a gardening section. Locate a bag of gardening soil with a label that lists the soil characteristics, such as nitrogen content and organic content, etc. Use the soil contents as a basis for discussing with your child the relationship between soil composition and soil function. For example: •  What are the properties of the soil? •  Is it light or dark in color? •  Is the texture rough and dry or wet and smooth? (Gardening soil is typically dark and damp.) •  Other than dirt, what components are in the soil? For help, have your child read the ingredients

on the bag. (Common answers include nitrogen, carbon, and phosphorous.) •  If the soil manufacturer had not added these things to the soil, how else could these materials

be added to soil? (One method is to compost organic material, and then add the results to soil.)

If you or a family friend has a garden at home, follow up this visit with a trip to the garden. Examine the soil with your child and discuss similarities and differences between the gardening soil in the garden store and the soil in an actual garden.