a complete project on volcano for class 9th
Answers
Answer:
volcano is a mountain that has, or had, lava (hot, liquid rock) come from a magma chamber under the ground.[1] Volcanoes are formed by the movement of tectonic plates.
Most volcanoes have a volcanic crater at the top. When a volcano is active, materials come out of it. The materials include lava, steam, gaseous sulfur compounds, ash and broken rock pieces.
When there is enough pressure, the volcano erupts. Some volcanic eruptions blow off the top of the volcano. The magma comes out, sometimes quickly and sometimes slowly. Some eruptions come out at a side instead of the top.
Volcanoes are found on planets other than Earth. An example is Olympus Mons on Mars.
Volcanologists are scientists who study volcanoes using methods from geology, chemistry, geography, mineralogy, physics and sociology.
The world's biggest volcano is named Mauna Loa in Hawaii. Mauna Loa is part of the five volcanoes on Hawaii's 'Big Island'. The most recent time this volcano erupted was in 1984. It erupted 33 times in the last 170 years. Like all the other Hawaiian volcanoes, Mauna Loa was created by the movement of the Pacific tectonic plate which moved over the Hawaii hotspot in the Earth's mantle. Mauna Loa is 4,196 meters tall. It is a shield volcano. The largest recent eruption from Mauna Loa left a lava trail 51 kilometres (32 miles) long
Explanation:
The lava and pyroclastic material (clouds of ash, lava fragments and vapor) that comes out from volcanoes can make many different kinds of land shapes. There are two basic kinds of volcanoes.
Shield volcanoes
Edit
These volcanoes are formed by fluid low-silica mafic lava.
Shield volcanoes are built out of layers of lava from continual eruptions (without explosions). Because the lava is so fluid, it spreads out, often over a wide area. Shield volcanoes do not grow to a great height, and the layers of lava spread out to give the volcano gently sloping sides. Shield volcanoes can produce huge areas of basalt, which is usually what lava is when cooled.
The base of the volcano increases in size over successive eruptions where solidified lava spreads out and accumulates. Some of the world's largest volcanoes are shield volcanoes.
Even though their sides are not very steep, shield volcanoes can be huge. Mauna Kea in Hawaii is the biggest mountain on Earth if it is measured from its base on the floor of the sea.[2]
Stratovolcanoes
Edit
Mount Fuji, an active stratovolcano in Japan that last erupted in 1707–08
Tavurvur, an active stratovolcano near Rabaul in Papua New Guinea
A stratovolcano, also known as a composite volcano,[3] is a tall, conical volcano. It is built up of many layers of hardened lava, tephra, pumice, and volcanic ash.
Unlike shield volcanoes, stratovolcanoes have a steep profile and periodic eruptions. The lava that flows from stratovolcanoes cools and hardens before spreading far. It is sticky, that is, it has high viscosity. The magma forming this lava is often felsic, with high-to-intermediate levels of silica, and less mafic magma. Big felsic lava flows are uncommon, but have travelled as far as 15 km (9.3 mi).[2][4]
Two famous stratovolcanoes are Japan's Mount Fuji, and Vesuvius. Both have big bases and steep sides that get steeper and steeper as it goes near the top. Vesuvius is famous for its destruction of the towns Pompeii and Herculaneum in 79 AD, killing thousands.
Caldera
Edit
Main article: Caldera
A caldera is a basin-like feature formed by collapse of land after a volcanic eruption. This happens after a huge stratovolcano blows its top off. The base of the crater then sinks, leaving a caldera where the top of the volcano was before. Krakatoa, best known for its catastrophic eruption in 1883, is much smaller now.
Answer:
PROJECT ON VOLCANO
Explanation:
Volcanoes are ruptures in the crust of our planet Earth that allow hot gases, molten lava and some rock fragments to erupt by opening and exposing the magma inside. In this piece of article, we will be discussing how and why volcanoes erupt.
How Do Volcanoes Erupt?
It is so hot deep within the earth that some rocks slowly melt and turn into a thick flowing matter known as magma. Since it is lighter than the solid rock around it, the magma rises and gets collected in magma chambers. Eventually, some magma pushes through fissures and vents in the earth’s surface. Hence, a volcanic eruption occurs and the erupted magma is known as lava.
We need to understand the Earth’s structure to know how volcanoes erupt. At the top lies the lithosphere, being the outermost layer that consists of the upper crust and mantle. The thickness of the crust ranges from 10km to 100km in mountainous locations and mainly consists of silicate rock. The video below will help you clearly understand the process of the volcanic eruption.
Why Do Volcanoes Erupt?
The Earth’s mantle within the crust is classified into different sections depending on individual seismology. These include upper mantle, that ranges between 8 – 35 km to 410 km; transition zone ranges from 400 to 660 km; lower mantle lies between 660 – 2891 km.
The conditions change dramatically from the crust in the mantle location. The pressures rise drastically and temperatures rise up to 1000 oC. This viscous and molten rock gets collected into large chambers within the Earth’s crust.
Since magma is lighter than surrounding rock, it floats up towards the surface and seeks out cracks and weakness in the mantle. It finally explodes from the peak point of a volcano after reaching the surface. When it is under the surface, the melted rock is known as magma and erupts as ash when it comes up.
Rocks, lava and ash are built across the volcanic vent with every eruption. The nature of the eruption mainly depends on the viscosity of the magma. The lava travels far and generates broad shield volcanoes when it flows easily. When it is too thick, it makes a familiar cone volcano shape. If the lava is extremely thick, it is capable of building up in the volcano and explode, known as lava domes.
