II. Distribution

Volcanoes (relationship among the locations of volcanoes, earthquake, epicenters, and mountain ranges)

             It is a feature in Earth’s crust where molten rock is squeezed out onto the Earth’s surface. Magma is the molten rock beneath the surface and it is called lava when it erupts, or flows out, from a volcano. Along with lava are the gasses, ash, and solid rock that are ejected on the Earth’s surface. The term volcano means that magma and other substances erupt on the surface, creating a landform of solidified lava and volcanic debris near the vent.

             Volcanoes can be found throughout the world. It comes in many different sizes and shapes but cone-shaped hills or mountains are the most common. Moreover, there are about 1,900 active volcanoes on Earth, meaning they are showing some level of activity and are more likely to erupt again. They are also called dormant volcanoes; they are the ones that show no current signs of exploding but at some point, are more likely to become active again in the future. While others are considered extinct.

             Volcanoes are an agent of change through volcanic eruption. They can create new landforms, but can also destroy everything. Volcanic eruption is a spectacular display of the Earth’s power. Yet, it can cause disastrous loss of life and property.

Active Volcanoes

• Active volcanoes are mountains that have craters on their sides or summits that spew lava, rocks, ash, and other materials are known as active volcanoes. The movement of tectonic plates beneath the surface of the Earth is the cause of these volcanic activities. 

Types of Volcanoes

Cinder cones – are steep, conical hills that have a prominent crater at the top. It is known as scoria cones. Scoria means having irregular-shaped, highly vesicular fragments of lava erupted in the air and are solid when they land. This type of volcano is surrounded by dark lava flows that erupt from their base. It frequently has an asymmetric shape in which it forms over a linear fissure vent and is elongated, and ones that are formed in areas with strong prevailing winds may be much taller on the downwind side.  

Composite Volcanoes (Stratovolcanoes) – it is the most picturesque among the types of volcanoes. It has a conical with a concave shape which is steeper near the top. They are active volcanoes for a long period, erupting periodically and generally, composed of lava flows, pyroclastic flows, mudflow deposits, and lava domes. They have multiple vents, but most of them have a main vent at the summit. Active composite volcanoes have a shallow magma chamber at depths of 3-6 miles (5-10 km). Thus, just like mountains, composite volcanoes are subjected to the forces of erosion. They may experience mass wasting events, including landslides, rock avalanches, lahars, and debris flows. In terms of its magma composition, it usually erupts a basalt to rhyolite, but intermediate (andesitic) and dacitic magmas are the most common.

Shield Volcanoes – are broad volcanoes with gentle slopes and are shaped somewhat like a warrior’s shield lying flat. Shield volcanoes have a convex shape as they are flatter near the summit. Also, they are constructed almost entirely of basaltic and/or andesitic lava flows which were very fluid when erupted and built by repeated eruptions over vast periods. The low viscosities of the erupted lavas create the great width of shield volcanoes relative to their height. It also produces thin widespread lava flows, eruptions from both the summit and fissure vents on the volcano’s flanks, and widening and subsidence along the summit and rift zones. Moreover, large shield volcanoes may have calderas that contain long-lasting lava lakes. They also have pit craters or smaller collapse structures, often with vertical sides.  

Earthquake Epicenters

         Earthquake is defined as the violent shaking of the ground which is produced by the sudden movement of rock materials below the Earth’s surface.

         When two blocks of the earth suddenly slip past one another, it results in an earthquake. The surface where they slip is called the fault or the fault plane. The hypocenter is the location below the earth’s surface where the earthquake starts. On the other hand, the epicenter is the location directly above the surface of the earth.

             There are different shocks of an earthquake. The foreshocks, mainshocks, aftershocks. A foreshock is a smaller earthquake that happens in the same place as the larger earthquake that follows. Meanwhile, the mainshock is the largest, main earthquake that can destroy infrastructures and properties. On the other hand, the aftershock is what follows after the mainshock. Aftershocks can continue for weeks, months, and even years after the mainshock. There are two ways in which we can measure the strength of an earthquake, it is the use of magnitude and intensity. Magnitude is the proportional energy released by an earthquake at the location. A seismograph is the instrument used in measuring the magnitude of an earthquake. Intensity, on the other hand, is the strength perceived and felt by people in a certain locality. It is a numerical rating represented by Roman Numerals that are based on the relative effects on people, the e
nvironment, and even the structure of the surroundings. The intensity of an earthquake is generally higher when it is near the epicenter.

Two Types of Earthquakes

          Tectonic Earthquake – this kind of earthquake occurs at plate boundaries. It happens when the large, thin plates of the Earth’s crust and upper mantle become stuck as they move past one another. As they lock together, pressure builds up. When they release, earthquakes occur. When two plates push into each other, they form a convergent plate boundary. 

       Volcanic Earthquake - it is much smaller than a tectonic earthquake and results from tectonic forces that occur in conjunction with volcanic activity. 

How does an earthquake happen?  

An earthquake is a shock wave from the underground that radiates to the Earth’s surface. It is caused by the sudden release of friction and pressure between tectonic plates. Earthquakes are a natural phenomenon that occurs frequently in certain areas of the world. Earthquakes cause a range of effects from unnoticeable, mild tremors to violent, prolonged shaking. The epicenter receives the most powerful shock waves and it is directly above the hypocenter. On the other hand, the hypocenter is the place in the underground where the earthquake begins.  

Mountain Ranges

Major Mountain Belts 

Mountain belts differ from one another, but they also have a number of similarities that enable Earth scientists to group them into certain distinct categories. 

Himalayas: A stunning mountain range spanning multiple nations in South Asia, including China, Nepal, Bhutan, and India. It is the result of the Indian and Eurasian plates colliding. The highest point on Earth is Mount Everest.. 

Andes: The South American Plate was subducted beneath the Nazca Plate, resulting in their creation. It is renowned for its deep valleys, active volcanoes, and stunning scenery. It extends through countries including Peru, Bolivia, Chile, and Colombia along South America's western coast.

Rocky Mountains: The North American Plate's uplift is what formed it. It passes through most of the United States and Canada as it travels across North America. Their breathtaking national parks, alpine lakes, and varied travel options have made them well-known. 

Alps: The African Plate colliding with the Eurasian Plate shaped them. The alpine regions of the world provide stunning scenery, snow-covered peaks, and top-notch skiing areas. They are a well-known mountain range in Europe that is spread throughout France, Switzerland, Italy, Austria, and Germany, among other nations. 

Andean Volcanic Belt: There are many active volcanoes there, and it runs parallel to the Andes. This stretches from southern Chile through Peru and Ecuador and is caused by the subduction of the Nazca Plate beneath the South American Plate. Japanese Archipelago: It arises from the Pacific Plate and Eurasian Plate convergent boundaries. It is made up of several volcanic islands in the Pacific Ocean, including the well-known Mount Fuji in Japan.