Activity 1: Hydrologic Cycle
Erosion creates three different types of river valleys, all of which are distinct and beautiful. These three different types of valley, their shapes and how they are formed will be discussed in this activity.
Instructional Method: Demonstration
Goal: To introduce the Hydrologic Cycle
Objectives: Students will be able to:
Preparation: 5 min.
The water we use today has been on Earth for hundreds of millions of years! Because Earth is a closed system, the total amount of water on the planet hasn't changed much since the beginning of time. Water moves around the world in three different forms: solid, liquid and vapor. It is constantly being used in all forms by people, plants, and animals but never really disappears.
The hydrologic cycle describes the journey of water as water molecules make their way from Earth's surface to the atmosphere and back again. This system, powered by the sun, is a continuous exchange of water between the oceans, the atmosphere, and the land. The same water you will drink tomorrow was probably also consumed by a dinosaur millions of years ago.
The Hydrologic Cycle: A brief introduction.
Evaporation: Water on Earth's surface returns to the atmosphere through evaporation. Surface water, such as lakes and oceans, is a major source of water for evaporation. Water may also evaporate from rivers, soil, glaciers, the skin of sweaty animals and other surfaces.
Transpiration: Plants return water to the atmosphere through transpiration. Plants draw water from the soil into their roots. The water moves through the stem, branches and leaves of the plant. Water is released through the leaves during photosynthesis and is evaporated from the surface of the leaf. Earth scientists often group evaporation and transpiration together using the term evapo-transpiration.
Condensation: Clouds form in the atmosphere through condensation. Water that returns to the atmosphere through evapotranspiration will condense as it cools at high elevations. Condensed water vapor can be seen in the form of clouds and fog.
Precipitation: When molecules of water vapor completely saturate the air, clouds are formed. When this same body of air quickly cools, the vapor condenses, forming water drops which merge and grow until they are too big to be suspended in the atmosphere by air currents. Depending on the temperature of the air through which these water droplets are falling, they will return to Earth as rain, snow, sleet or hail.
Runoff: Runoff is the process of rain being funneled across the surface of Earth into streams, rivers and eventually lakes and oceans. Runoff can happen both on Earth's surface and underground. Not all water that hits Earth's surface will immediately become runoff. Some water soaks into the soil. This process is called infiltration. (Some teachers may prefer to present infiltration as a separate step in the water cycle.) Water can still move downhill under the soil. Water that soaks deep into the ground, penetrating underground rock layers, is called groundwater. Groundwater also flows downhill, although very slowly. It can take hundreds of thousands of years for groundwater to reach a lake or ocean!
Together these five processes make up the Hydrologic Cycle.
They have just created a small world where the Hydrologic Cycle has occurred.
How does your small world differ from the real world? What does the Hydrology Cycle mean to living things on the Earth?
Included National Parks and other sites:
Utah Science Core:
4th Grade Standard 1 Objective 1,2
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