The topography, or surface of the Earth, is constantly changing shape due to many powerful forces. In this lesson, we will learn about some of the amazing changes that occur on Earth due to the processes of weathering, erosion, and deposition.
What Is Topography?
Have you ever had a brand-new eraser? If so, you probably noticed that over time and with regular use, its shape changed. What forces caused this? Just like an eraser, the surface of the Earth can also change shape.
Topography is the shape of the Earth's surface and its physical features, such as mountains, valleys, canyons, and other landforms. In this lesson, we will explore Earth's topography and how it is continuously being reshaped due to many powerful processes that break it down and build it up.
Nature is powerful and it can break down even the hardest rock or mineral on Earth. Weathering is the wearing away of rock or soil by wind, water, or any other natural cause. There are two types of weathering: mechanical and chemical.
Mechanical weathering occurs when a force, such as water, wind, or ice, moves soil or breaks rocks into smaller pieces. When water moves across rocks, it causes them to break down. When it flows into cracks in rocks and freezes, the ice causes them to split and break apart.
Extreme temperature changes cause rocks to expand and contract, which makes them weaken and break apart. Sand is created when crashing waves break rock apart into tiny pieces. Plant roots, animals pushing up or digging through the Earth, and even gravity, which can trigger avalanches, can cause rock and soil to move.
In chemical weathering, the chemical makeup of the rock is permanently changed due to reactions between rocks and chemicals, such as oxygen or carbon dioxide. Humans and animals release carbon dioxide when they breathe, which, when mixed with water, creates a type of acid that breaks down rock. Acid rain is caused when chemicals from air pollution mix with rainwater and is a type of chemical weathering that can dissolve rock. The Carlsbad Caverns in New Mexico were formed as a result of chemical weathering.
Erosion occurs when pieces of Earth that have been weathered and worn away are moved to another place. Wind can carry soil and rock far distances. Along the way it can blast the sides of rocks and mountains, changing their shape. Glaciers, which are huge moving masses of ice and snow, can scrape against rock and soil and carry it away.
Water, in the form of rain, rivers, and waves, causes erosion of rock and soil. Erosion changes the shape of coastlines, mountains, and many other landforms. All rocks on the Earth are vulnerable to weathering and erosion. You need only look at a picture of the Grand Canyon in Arizona to understand how powerful these processes are!
Deposition of Sediment
Getting back to the eraser example, you probably noticed the pesky little bits of rubber that came off onto your paper when you rubbed the eraser against it. This is like sediment or pieces of the Earth that have been broken off by erosion. Chances are that you brushed them off onto the floor or into the wastebasket.
This is similar to the process of deposition, which happens when Earth material that has been eroded is placed, or deposited, in another area. The deposition of sediment can create many new landforms. It is responsible for the formation of certain types of islands, sand dunes on beaches and in deserts, and river deltas.
Natural disasters, like tsunamis, floods, volcanoes, earthquakes, avalanches, and landslides, also reshape topography. These powerful events cause weathering, erosion, and deposition due to rushing water and sediment or enormous pressure pushing or pulling on Earth's surface. While the processes of weathering, erosion, and deposition can happen slowly over time, natural disasters can forever change the shape of Earth's surface in a quick and often devastating way.
- Topography is the shape of the Earth's surface and its physical features. Topography is constantly being reshaped by weathering, erosion, and deposition.
- Weathering is the wearing away of rock or soil by wind, water, or any other natural cause.
- In mechanical weathering, the shape and size of the rock changes due to water, wind, or ice moving soil or breaking rocks into smaller pieces.
- Chemical weathering occurs when the chemical makeup of the rock is permanently changed due to reactions between rocks and chemicals, like those found in acid rain.
- Erosion is the wearing away of Earth's surface, where it is moved, or deposited, to another place.
- Sediment is pieces of Earth's surface that have been broken off.
- Deposition occurs when sediment that has been eroded is moved to another place and is a process that can create new landforms.
- Natural disasters, such as tsunamis, floods, volcanoes, earthquakes, avalanches, and landslides, are all dramatic events that can quickly reshape topography.
As you approach the end of this lesson, you might have developed the ability to:
- Define key vocabulary terms related to topography and weathering, including weathering, erosion, and deposition of sediment
- Detail some natural disasters that can affect topography