Most changes to Earth happen very slowly over thousands or millions of years. Wind and water slowly wear away rocks. Rain and rivers carry soil from one place to another. But Earth can also change suddenly and dramatically. Scientists call these fast changes or sudden geological events. The three most important fast changes are volcanoes, earthquakes, and landslides.
A volcano is an opening in Earth's crust where hot molten rock called magma rises to the surface. When magma reaches the surface, it is called lava. Volcanic eruptions can blast lava, ash, and gas high into the air. Some eruptions are gentle and slow, while others are explosive and powerful. Volcanoes can create new land, change river paths, and cover entire towns with ash. The Ring of Fire is a large area around the Pacific Ocean where most of the world's volcanoes are located.
An earthquake is a sudden shaking of the ground caused by movement deep underground. Earth's outer shell is made of huge pieces called tectonic plates. These plates are always moving slowly, sometimes rubbing past each other, sometimes pushing together, and sometimes pulling apart. When plates get stuck and then suddenly release, the energy shoots out in all directions as seismic waves, causing the ground to shake. Scientists measure earthquakes with a seismograph and rate their size on the Richter scale.
A landslide is when rock, mud, and soil move rapidly down a slope. Heavy rain, earthquakes, or volcanic eruptions can trigger landslides. When the ground becomes soaked with water, it becomes heavy and loses its grip on the hillside. Landslides can move very fast and carry enormous amounts of material. They can bury roads, destroy buildings, and change the shape of the landscape in just minutes.
1. What are the three main types of fast changes to Earth?
2. What is magma and what is it called when it reaches the surface?
3. What causes an earthquake?
4. Describe how a landslide is triggered and what it can do to the landscape. Explain why heavy rain can cause landslides.
Write a definition or draw a picture for each word.
Read each event. Write FC for fast change or SC for slow change.
| Event | Fast or Slow? |
|---|---|
| A volcano erupts and sends lava flowing down a mountain. | |
| Wind slowly wears away a sandstone cliff over hundreds of years. | |
| Heavy rain causes mud and rocks to slide down a steep hillside. | |
| A river slowly carves a canyon through rock over millions of years. | |
| The ground shakes suddenly during an earthquake. | |
| Rain and water slowly move soil from a hillside to a valley. |
Fill in the comparison chart for each fast change.
| Type | What Causes It? | What Happens? | How Quickly? |
|---|---|---|---|
| Volcano | |||
| Earthquake | |||
| Landslide |
Draw a volcano, an earthquake, and a landslide. Label each drawing.
Volcano — show lava and ash.
Earthquake — show buildings shaking.
Landslide — show material moving downhill.
Which fast change do you think would be the most dangerous to someone living nearby? Explain your reasoning.
1. Most changes to Earth happen slowly over long periods of time.
2. Magma is called lava when it reaches the surface.
3. Earthquakes are caused by wind blowing across the surface.
4. Tectonic plates are huge pieces of Earth's outer shell.
5. A seismograph measures the size of earthquakes.
6. Landslides can be triggered by heavy rain or earthquakes.
7. The Ring of Fire is located around the Atlantic Ocean.
8. Volcanoes can create new land and change the landscape.
Word Bank: volcanolavaearthquakelandslidetectonic platesseismographseismic wavesmagma
1. An opening in Earth's crust where molten rock rises is a ________________.
2. Molten rock is called ________________ before it reaches the surface.
3. When magma reaches the surface, it is called ________________.
4. A sudden shaking of the ground is an ________________.
5. Earth's outer shell is made of huge pieces called ________________.
6. Energy that travels through the ground during an earthquake are ________________.
7. A tool that measures earthquakes is a ________________.
8. When rock and soil move rapidly down a slope, it is called a ________________.
Look for signs of both fast and slow changes in your area. Write down what you find.
| What You Looked For | Fast or Slow Change? | What You Found |
|---|---|---|
| Cracks in the ground or pavement | ||
| Eroded hillsides or gullies | ||
| Weathered rocks or crumbling walls | ||
| Any other Earth changes |
Imagine you live near an active volcano. What are some things you might see or feel before or during an eruption? What could you do to stay safe?