Wednesday
Earthquakes: The Power Beneath Our Feet
The Earth’s surface is made up of enormous slabs of rock called tectonic plates. These plates float on a layer of hot, semi-molten rock known as the mantle. Although the plates move very slowly — often just a few centimetres each year — their movement shapes the planet over millions of years. Mountains form, oceans widen, and continents drift apart.
Sometimes, however, tectonic plates do not slide smoothly past one another. At the boundaries where they meet, friction can cause them to become stuck. As the plates continue to push, pressure builds up deep underground. Eventually, this pressure becomes too great and is suddenly released, sending powerful energy waves through the Earth. These waves cause the ground to shake, which we experience as an earthquake.
Most earthquakes occur along fault lines, which are cracks in the Earth’s crust where plates meet. One of the most well-known fault lines is the San Andreas Fault in California, USA. This region experiences frequent earthquakes, some of which have caused major damage to cities and infrastructure.
The size of an earthquake is measured using the Richter scale, which records the amount of energy released. Each increase on the scale represents an earthquake that is ten times stronger than the previous number. For example, a magnitude 6 earthquake is ten times more powerful than a magnitude 5. Strong earthquakes can cause buildings to collapse, trigger landslides, and even change the shape of the land.
When earthquakes occur beneath the ocean floor, they can push enormous amounts of water upwards, creating giant waves known as tsunamis. These waves can travel across entire oceans at great speed and cause flooding when they reach land. Some tsunamis have destroyed coastal towns and affected countries thousands of kilometres away from where the earthquake first happened.
Scientists called seismologists study earthquakes to better understand how and why they occur. They use sensitive instruments known as seismographs to detect even the smallest movements in the Earth’s crust. Although predicting the exact time and place of an earthquake is still impossible, scientists can identify areas at high risk and help communities prepare by designing stronger buildings and emergency plans.
Answer the following retrieval questions in your Early Morning Book.
1. What are tectonic plates made of?
2. On what layer do tectonic plates float?
3. How fast do tectonic plates usually move each year?
4. What causes pressure to build up at plate boundaries?
5. What happens when this pressure is released?
6. Where do most earthquakes occur?
7. Name the fault line mentioned in the text.
8. What does the Richter scale measure?
9. How much stronger is a magnitude 6 earthquake than a magnitude 5?
10. List two effects of strong earthquakes mentioned in the text.
11. What can underwater earthquakes create?
12. How far can tsunamis travel?
13. What tools do seismologists use to detect movement?
14. Can scientists predict earthquakes exactly?
15. How do scientists help communities prepare?