LESSON 4: WATER CYCLE AND ROCK CYCLE

What is the Water Cycle?The Earth is the only habitable planet in our solar system. It is the only planet that has life and can support life. The Earth has many systems that work together and interact. The major systems on Earth can be described as the four “spheres”, the four dynamic zones. Each of the four spheres work with each other to create a habitable planet.

Shape and change the Earth’s surface. Destroy the old and create the new. Protect the Earth. Support ecosystems for life.

The geosphere is the zone of the Earth that includes all of the solid physical parts of the Earth like rock, minerals, soils, landforms, landscapes, and even the interior zones of the Earth. The hydrosphere is the zone of the Earth that includes all of the water-filled zones like oceans, rivers, ice, and groundwater. The biosphere is the zone of the Earth that includes all of the living things, like plants and animals and their ecosystems. The biosphere crosses all of the other spheres. The atmosphere is the envelope of gas that surrounds the Earth from the Earth’s surface to the edge of space. Earth’s atmosphere includes the air, plus the weather and climate.

Gases

Water

Solid surface

Living

All of the systems on Earth are interconnected. If one system or sphere is affected negatively by human impacts (like pollution or ecosystem destruction) or by natural disasters (hurricane or wildfire), the other spheres will feel the effect of the negative impact.

For example, a volcanic eruption in the geosphere will expel ash and toxic gases into the atmosphere, which then can rain into the rivers and oceans affecting the hydrosphere. This creates adverse conditions for the organisms (biosphere) near the volcano.

The Earth is called “the blue planet” because it is the only body in the solar system with liquid water at its surface. (see picture at left).

71% Earth’s surface covered by oceans.29% Earth’s surface covered by the continents.

The Water CycleWater Cycle

Water is mobile within Earth’s interconnected spheres by the process of the water cycle. The water cycle is model that describes the continuous transformation of water (changing forms) and movement of water over the surface of the Earth. Water moves from hydrosphere to atmosphere to biosphere and to geosphere in many different pathways. Sunlight supplies the energy that drives the transformations of water and the movement of water between the four spheres. There is neither a beginning nor end to the water cycle because all processes happen at the same time, but not necessarily at the same rate. The diagram to the left shows the water cycle model and all of its component processes.

Evaporation is the transformation of liquid water into water vapor (water gas) by the addition of heat energy from the Sun. Evaporation moves water from the hydrosphere (like oceans, rivers, and lakes) to the atmosphere.

Condensation is the transformation of water vapor into liquid water when the water vapor releases heat to the environment around it. The air in the atmosphere is cooler than the air near the ground. As the water vapor rises into the atmosphere, the water vapor cools by releasing its heat to the colder air around it. Billions and billions of tiny water droplets form, the result is cloud formation. Clouds are buoyant floating masses of tiny water droplets and ice crystals in the sky.

Transpiration is the release of water vapor from the leaves of plants and trees to the atmosphere. Transpiration moves water from the biosphere to the atmosphere. Transpiration is a natural process, but can be accelerated (move faster) during dry, hot daytime hours.

Precipitation is liquid water (rain) or solid water (ice or snow) that falls from the sky to the ground. Precipitation forms when the water droplets in the clouds grow larger and larger, and become too heavy to remain floating in the sky. Precipitation moves water from the atmosphere to the geosphere, or from the atmosphere to the hydrosphere.

Runoff is the movement of water by rivers and streams from the continents back to the oceans. After precipitation falls on the land, the water flows into channels and moves by gravity downslope to the oceans. Runoff moves water from the geosphere to the hydrosphere.

Infiltration and percolation are processes where the ground soaks up water from surface of the ground. Water will slowly move downward, or seep, into the rock and soil beneath. Water underground is called groundwater. Groundwater moves very slowly under the influence of gravity. Groundwater is important because it is a vast source of freshwater for humans to use. Percolation moves water from the surface of the geosphere to the subsurface of the geosphere.

Consumption or uptake is when plants use their root systems to extract water from the soil or ground. Plants use this water for their biological needs, including photosynthesis. Consumption moves water from the geosphere to the biosphere, or from the hydrosphere to the biosphere.

What is the Rock Cycle?

The rock cycle is a simplified model that describes how rocks in the Earth’s crust move and are changed by forces and heat from one type of rock to another type of rock. The rock cycle is closely tied to plate tectonics and volcanism (constructive forces), and to weathering and erosion (destructive forces) of rock exposed at the Earth’s surface.

The diagram above shows a simplified rock cycle. The arrows show the pathways and forces that cause the rock types to change from one type of rock to another type of rock. There are three types of rock: igneous rock, sedimentary rock, and metamorphic rock.

Igneous rocks Rocks that begin from a molten state (hot and melted), and cools to solid rock. Igneous rocks form from magma and lava.

Sedimentary rocksRocks that form from the deposition, consolidation, and compaction of sediments. Sedimentary rocks usually form in deep bodies of water as sediments accumulate into very thick layers.

Sediments Small weathered fragments of rock. Sediments are created by the weathering and erosion of rock that is exposed at the Earth’s surface.

Metamorphic rocksRocks that are “changed rock”. Extreme heat and pressure will change existing rock into a new type of rock with totally different physical and chemical properties.

Metamorphism The change of a rock due to extreme heat and pressure put upon the rock.

Igneous rocks harden from lava and magma. All igneous rocks start as molten (hot and melted) and harden to solid rock. The original rock can be another igneous rock, a sedimentary rock, or a metamorphic rock. When extreme heat melts the original rock, it forms magma or lava. When the magma cools and hardens, it becomes a new igneous rock.

Igneous rockor

Sedimentary rockor

Metamorphic rock

Heat andmelting Magma

or lava Cools to newIgneous rock

Sedimentary rocks form from sediments. Sediments are small particles of rock that form when rock at the surface of the earth is weathered and broken into smaller and smaller pieces by the wind, rain, and ice. The sediments are eroded and transported from the land by blowing wind and flowing rivers into the ocean. The sediments are deposited in thick layers in the deep water. Over thousands and millions of years, the sediments are compacted and cemented together into new layers of sedimentary rocks.

Igneous rockor

Sedimentary rockor

Metamorphic rock

Weathering and breaking down into sediments

Erosion and transport by wind and rivers

Deposited in the ocean, compacted and cemented into thick layers

New sedimentary rock forms

Metamorphic rocks are “changed rocks”. The original rock is subject to extreme heating and pressure, most likely by volcanic or plate tectonic forces, and changes into a metamorphic rock. Metamorphic rocks differ in physical and chemical properties to the original rock from which they started. Even though heat causes the rock to change, the heat cannot be too great to melt the rock, otherwise it will become a new igneous rock.

Igneous rockor

Sedimentary rockor

Metamorphic rock

Heat and pressure by plate tectonic forces or by heat from nearby volcanism

Rock changes into a new metamorphic rock

Learning Objectives: What every student should know or be able to do to master the content in Water Cycle and Rock Cycle.

1. Students should be able to describe verbally and describe in writing the mechanisms that move and change water on the surface of the Earth.

2. Students should be able to use diagrams and flow charts to identify the process that move water from sphere to sphere in the water cycle.

3. Students should be able to describe verbally and describe in writing the mechanisms that move and change rock as part of the rock cycle.

4. Students should be able to use diagrams and flow charts to identify the processes as part of the rock cycle.

Academic vocabulary: Students must know and use the following vocabulary correctly in order to achieve content mastery.

Water cycleAtmosphereGeosphereBiosphereHydrosphereEvaporationTranspirationCondensationConsumption (uptake)InfiltrationGroundwater

RunoffPrecipitationIgneous rockMetamorphic rockSedimentary rockSedimentWeatheringErosionTransportCompaction & cementation