Earth Materials and Water Flow

Water moves around the planet, powered by energy from the sun and gravity. As it cycles from one form to another, it influences weather and climate, connecting all of Earth’s systems. In this lesson, students use this knowledge to analyze how Earth’s systems interact in the water cycle, focusing on the interactions of the geosphere and the hydrosphere as they test different materials to determine which is most permeable to water.  

• Scientists study small sections, called systems, to understand how everything works. A system is a set of connected, interacting parts that form a more complex whole. 
• The water cycle is the circulation of water from a collection to the atmosphere and back to the surface.
• Water on Earth is constantly cycling from one state to another, depending on the amount of heat from the sun. This movement of water connects all of Earth’s systems.
• The largest aquifer in the United States is called the Ogallala Aquifer, and it sits beneath eight states in western United States. The Ogallala Aquifer plays in the lives of people who live in the high plains region.  
• Groundwater is the supply of fresh water found beneath Earth’s surface in the pores of soil, sand, and rock. Groundwater is the result of two interacting systems: the hydrosphere and the geosphere.
• Rocks that are both porous and permeable are most likely to hold water. Porosity refers to the number of spaces between particles in a substance. Permeability refers to the ease with which substances such as water move through a material.
  
  

• How does water interact with the atmosphere?
• Why does water on Earth cycle between a solid, liquid, and gas?
• How is groundwater a result of interacting systems?
• What happens to water once it falls to Earth’s surface?
• How does water end up underground?
• How does the rock cycle influence groundwater?  
• Which properties determine how likely a rock is to hold water?
• Why is groundwater an important source of freshwater? Why is groundwater often very pure, without many pollutants?  
• Why is the Ogallala Aquifer running out of water?  

Misconception: The energy that people use does not come from natural resources.

Fact: Energy resources come from the environment, including fossil fuels, wind, water, and solar.

Misconception: Science and engineering are completely separate from each other.

Fact: Science and engineering are interconnected. Engineers use knowledge gained from scientists to design technologies that solve problems. Scientists can then use those technologies to ask deeper questions.

Aquifer:  the underground layer of rock, sand, or soil that holds groundwater

Climate: the average weather over a span of 30 years

Permeability:  the ease with which substances such as water move through a material

Porosity: the number of spaces between particles in a substance

System: a set of connected, interacting parts that form a more complex whole

Water cycle:  the circulation of water through the hydrosphere from Earth’s surface to the atmosphere and back

Weather:  the conditions of the atmosphere (temperature, humidity, wind speed, air pressure, and precipitation) in a particular place at a particular time

Filtration

Groundwater isn’t an underground river. Instead, it is water that fills the spaces between soil particles and rock. Because of this, it is some of the cleanest water on Earth. This is because the particles of rock that make up aquifers act as a natural filter as water moves through the layers of materials.

Picture a coffee pot. Hot water is poured into the pot, where it mixes with coffee grounds. A coffee filter then traps the coffee grounds and allows liquid coffee to flow through.

Coffee filters work because they have pores that are large enough for water to travel through but small enough that coffee grounds cannot.

Aquifers work in the same way as coffee filters. As gravity pulls water from Earth’s surface underground, the water is filtered, becoming purer. Some aquifers have cleaner water than other aquifers because they are better able to filter out contaminants as water moves through them.

Earth Systems

Groundwater is the result of two interacting Earth systems. A system is a set of connected, interacting parts that form a more complex whole. Scientists study Earth’s systems to understand how the different parts interact with and influence one another.

The hydrosphere is the system made up of all of the water found on Earth. The geosphere is made up of Earth’s landforms, including rocks and soil. As water moves over Earth’s surface, it shapes the geosphere. It does this by weathering and eroding the rocks and soil it passes over.

The hydrosphere is also affected by the geosphere because not all rocks store water. The processes that shape and re-form rocks in the rock cycle determine how likely a rock is to store water.

How Does Water Get Underground?

Rocks that are both porous and permeable are most likely to hold water. Porosity refers to the number of spaces between particles in a substance. It determines how much water a material can hold. Permeability refers to the ease with which substances such as water move through a material. It determines whether water can move through the material.

Some of the water in the Ogallala Aquifer has been stored there for millions of years. It got there when water on Earth’s surface seeped into the ground.

For the hands-on activity in this lesson, students carry out an experiment to determine how the particle size of an Earth material affects its permeability to water. Students collaboratively plan and conduct an investigation that compares how fast water moves through equal volumes of soil, sand, and gravel to see which is most permeable to water.