DE Science Elementary School Earth’s Changing Surface Review

Formation of Landforms—The Key Ideas Wind, water, and ice shape the Earth by transporting rocks and soil across Earth's surface. Canyons are carved from the landscape over a long period of time by rivers eroding away rock. Dunes form as winds cause sand to pile up. The sand can come from such sources as rock falls from sea cliffs, or sand can be transported hundreds to thousands of miles by streams, rivers, and oceans. Deltas are located at the mouth of a river that flows into a larger body of water. The river slows and the sand drops out of the flow, building up over time to form a delta. Human activities can impact landforms. For example, Dams and levees can block the flow of sedimentary materials into a delta, preventing it from replenishing itself.

Formation of Landforms—Using DE Science Content Exploration: Forces That Shape the EarthForces That Shape the Earth Video Segment: Eroding Power of Swiftly Flowing Streams: Gorges, Canyons, and ValleysEroding Power of Swiftly Flowing Streams: Gorges, Canyons, and Valleys Video Segment: Castleton Tower: Clues in the RockCastleton Tower: Clues in the Rock Video Segment: Scientists’ WarningsScientists’ Warnings

Waters of the Earth – The Big Ideas Lakes, ponds, streams, rivers, and wetlands are all freshwater. Lakes and ponds form where water lies in low areas. Streams and rivers form where rain or snowfall run off from higher areas to lower areas. Rivers flow into oceans, lakes or estuaries. Estuaries are river basins that have become lower than sea level and have a mix of saltwater and freshwater. Both estuaries and wetlands serve as protective areas where small organisms and young organisms can survive. Wetlands can contain saltwater, freshwater, or brackish water, which is a combination of both. Wetlands form near the edges of larger bodies of water or when a lake, pond, or estuary becomes very shallow. Ocean basins are large low areas of Earth filled with saltwater. The sea floor has mountains, plateaus, and plains.

Waters of the Earth – Using DE Science Content Exploration: Waters of the Earth Video: What Is It Like at the Bottom of the Ocean? E Book: Earth’s Oceans

Glaciers – The Big Ideas A glacier is a large mass of moving ice that exists all year. During the last ice age, a glacier covered much of North America. Glaciers are one cause of large-scale erosion and deposition, leaving a valley as a result. Glaciers normally expand or contract over thousands years. In recent decades, many glaciers have shrunk significantly.

Glaciers – Using DE Science Content Exploration: GlaciersGlaciers eBook: The Life Cycle of GlaciersThe Life Cycle of Glaciers Video: GlaciersGlaciers

Time Line in Geology – The Big Ideas Scientists divide Earth’s history into a geologic time line. In geologic time the smallest units are measured in millions of years. A million years is such a long time that it is hard to comprehend. The fossil record covers hundreds of millions of years in Earth’s history.

Time Line in Geology – Using DE Science Content Exploration: Time line in Geology Video: Organizing Earth’s Past E Book: Earth’s Time Line

Life on Earth Over Time – The Big Ideas The fossil record shows that Earth’s species have adapted and changed over millions of years. The theory of evolution is based on the fossil record and observations of species adapting and changing. Sudden changes in the fossil record indicate that mass extinctions killed off some species. The most widely accepted theory for mass extinctions is a rapid change in the environment from the impact of large meteors on Earth. The fossil record shows that modern humans have existed for much less than a million years.

Life on Earth Over Time – Using DE Science Content Exploration: Life on Earth Over Time Virtual Lab: No Bones About It Video: Theories About Why Dinosaurs Became Extinct

Frozen in Time – The Big Ideas Some organisms have been found completely intact, frozen in glaciers. Ice cores from the Arctic and Antarctic contain evidence of living things and climate conditions from tens of thousands of years ago.

Frozen in Time – Using DE Science Content. Exploration: Frozen in Time Reading Passage: Drilling Back in Time Video: The Wooly Mammoth

Fossils – The Big Ideas Fossils are the remains, imprints, or traces of prehistoric organisms. The rock layer containing a fossil provides information about a fossil’s age. Fossils form when remains are replaced with minerals or an organism leaves space in sediment. Preserved footprints, trails, or burrows of prehistoric animals are trace fossils. A fossil may give information about an area’s environment during a period of Earth’s history.

Fossils – Using DE Science Content Exploration: Fossils Reading Passage: Make Your Own Fossil Video: What Are Fossils?

Rocks – The Big Ideas Rocks can be broken down into smaller pieces. Rocks are made up of one or more than one mineral. Based on how they are formed, rocks are classified into three groups: sedimentary, igneous, and metamorphic. Sedimentary rocks are made up of tiny pieces of shells, rocks, sand, or other materials. Igneous rocks are made when melted rock cools and hardens. Metamorphic rocks form under heat and pressure. When rocks are created, changed, and destroyed, it is called The Rock Cycle.

Rocks – Using DE Science Content Exploration: RocksRocks Video: Rocks: An IntroductionRocks: An Introduction Video: The Rock CycleThe Rock Cycle

Fossil Fuels – The Big Ideas Much energy comes from burning fossil fuels in electric power plants and automobiles. Unless used carefully, fossil fuels produce pollution as they are burned. Fossil fuels are a non-renewable energy resource from a limited supply. Coal, petroleum, and natural gas are fossil fuels formed from the remains of plants and animals. Conserving energy helps save non-renewable resources and reduces pollution.

Fossil Fuels – Using DE Science Content Exploration: Fossil FuelsFossil Fuels Virtual Lab: How Big is Your Footprint?How Big is Your Footprint? Video: What Are Fossil Fuels?What Are Fossil Fuels?

Sunlight – The Big Ideas Sunlight is the source of energy for heat and light on Earth. Energy in almost every plant and animal originates from the sun. Sunlight is a renewable resource. Humans capture and use sunlight directly, but we are still trying to improve our methods.

Sunlight – Using DE Science Content Exploration: Sunlight Virtual Lab: How Big is Your Footprint? Video: Trapping the Sun’s Energy

Alternative Energy Resources— The Key Ideas We can get energy from a variety of natural resources. Renewable energy resources can be replenished by natural processes. Common renewable energy resources include wind, solar, hydroelectric, geothermal, and biofuels.

Alternative Energy Resources— Using DE Science Content Exploration: Power Up Virtual Lab: How Big Is Your Footprint? Video: Alternatives to Fossil Fuels