Introduction:

You may have heard about the recent seismic activity in the offshore area of Al-Shaqra, west of Al-Madinah. This region experiences seismic and some minor volcanic activities. But what are earthquakes? And what about volcanoes? Earthquakes are the shaking of the Earth's crust. When earthquakes occur, the ground shakes, items fall off shelves, roads crack, and buildings, bridges, and columns may collapse. Even water pipes can rupture.

Article elements:

1. What are Earthquakes?
2. The Strength of Rocks to Withstand:
3. Determining the Epicenter:
4. How to measure the strength of an earthquake?
5. Tsunamis:
6. Safety from earthquake hazards:
7. What are volcanoes, and how do they shape the Earth's surface?
8. What is weathering?
9. Physical weathering:
10. Chemical weathering:
11. Erosion and Deposition:
12. Deposition:
13. Conclusion:

What are Earthquakes?

The features of the Earth's surface are shaped by a variety of processes, some occurring beneath the Earth's surface, known as internal processes, including earthquakes and volcanoes. Earthquakes occur due to the movement of tectonic plates. The Earth's plates move steadily and slowly, and when two adjacent plates stop moving due to friction in a specific area, stored energy builds up until it reaches a certain point, causing an increase in energy.

The Strength of Rocks to Withstand:

Rocks break along a fault zone, and the plates move rapidly and unexpectedly, releasing stored energy in the form of violent waves that cause the Earth's crust to vibrate. This vibration is called an earthquake, and the waves causing it are called seismic waves. Earthquakes can occur at depths of up to 644 km, but most occur at depths less than 80 km. The location under the Earth's surface where the earthquake originates is called the earthquake focus. Seismic waves spread out from the earthquake focus in all directions. When they reach the Earth's surface, they spread from the point directly above the focus. This point is called the epicenter.

Determining the Epicenter:

The epicenter of an earthquake is determined by monitoring the arrival time of seismic waves at three observation stations. This allows calculating the distance between the epicenter and each station. Circles are drawn on the map at the locations of the three stations, centered on the station's location, with a radius equal to the distance traveled by the seismic waves. The intersection point of these three circles is the epicenter of the earthquake.

How to measure the strength of an earthquake?

Earthquakes vary in strength and destructive effects. The strength of an earthquake is estimated by the amount of energy released during its occurrence. The Richter scale is used for this purpose, starting from a measurement of 1. An increase of one degree in earthquake strength indicates 30 times more released energy. For example, a magnitude 7 earthquake on the Richter scale releases 30 times more energy than a magnitude 6 earthquake and 900 (30 x 30) times more energy than a magnitude 1 earthquake on the same scale.

Tsunamis:

When earthquakes occur at the ocean floor, waves move in all directions at very high speeds ranging from 500 to 1000 kilometers per hour, carrying tremendous energy. As they approach the coasts and shallow-water areas, the volume of water moving due to seismic energy decreases significantly compared to the deep ocean. This sudden reduction in water volume leads to a rapid increase in wave height, transforming them into giant waves that collide with the shore, causing destruction. These waves are called tsunamis.

Safety from earthquake hazards:

Humans cannot prevent earthquakes, but precautions can be taken to reduce the risks associated with them. This includes specifying building standards, distributing educational pamphlets, and training citizens on the necessary procedures to follow during an earthquake.

What are volcanoes, and how do they shape the Earth's surface?

A volcano is an opening in the Earth's crust from which magma, gases, and volcanic ash erupt to the surface. Magma, when it reaches the Earth's surface, is called lava. Most volcanoes occur along the boundaries of tectonic plates, whether on land or on the ocean floor. During a volcanic eruption, lava accumulates around the volcano's vent, forming a conical shape with the vent at its summit. With repeated volcanic eruptions, material accumulates, and the cone's height increases. A volcano can have more than one vent, and volcanic vents may lead to the formation of volcanic craters. There are three types of volcanoes: active, which are still erupting, dormant, which has stopped erupting but may erupt again, and extinct, which is unlikely to erupt again.

What is weathering?

Have you ever placed a fully filled water bottle in the freezer? What happened to it? The water froze, leading to the bottle's breakage. This is similar to what happens when water enters the cracks in rocks and freezes, causing the rocks to break into smaller pieces. This process of breaking down rocks or other materials is called weathering, which occurs in two main types: physical weathering and chemical weathering.

Physical weathering:

Physical weathering refers to the breakdown of rocks without a change in their chemical composition. Factors contributing to physical weathering include the freezing of water in cracks, the growth of plant roots causing pressure, and temperature changes.

Chemical weathering:

Chemical weathering occurs due to the interaction of chemical substances in water or air with the minerals in rocks, leading to the formation of new minerals and reshaping the Earth's surface. Groundwater carrying chemicals can affect underground rocks, causing them to break and form caves. Acid rain is a significant factor in chemical weathering, affecting certain types of rocks and altering their chemical composition. It also affects historical structures and other constructions.

Erosion and Deposition:

Look at the picture below and ask yourself: How is the course of the Nile River in this picture? What does the water carry to make its color turn brown? When rain falls on the ground and flows on the surface, water mixes with the soil and carries silt and clay. When the water quantity increases, it flows with force, carrying everything in its path, including trees, rocks, and soil. This way, rock fragments and soil are transported to distant places. The process of moving soil and rock fragments from one place to another on the Earth's surface is called erosion. Natural factors causing erosion include flowing water, winds, glaciers, and sea waves.

Deposition:

After the speed of erosion factors (rivers, glaciers, winds, etc.) decreases, the rock and sediment fragments are deposited away from the areas where they were carried. This process of depositing rock fragments is called deposition. Weathering and deposition together change the Earth's surface, making some prominent features disappear, such as mountains and hills, while giving rise to new landscapes, including river deltas, sand dunes, and rock layers.

Conclusion:

1. Seismic and volcanic activity play a crucial role in shaping the Earth's surface, reflecting immense natural forces that control geographical formations.

2. Earthquakes represent vibrations in the Earth's crust resulting from the movement of tectonic plates.

3. Volcanoes act as vents for the release of magma and gases from the Earth's interior, playing a role in reshaping landscapes and forming new regions.

4. Physical and chemical weathering demonstrate how the breakdown of rocks influences the Earth's surface, with water, wind, and other natural factors transporting and depositing rock fragments in new areas.

5. Understanding these geological processes helps humans take measures to mitigate the risks associated with earthquakes, volcanic eruptions, and the changing landscape.

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