1. Context

 Hawaii's Mauna Loa, the world's largest active volcano, is erupting for the first time in nearly 40 years – causing spectacular scenes, casting an eerie red glow over the island and shooting lava up to 200ft (60 meters) in the air

2. About Mauna Lao

• Mauna Loa is one of five volcanoes that together make up the Big Island of Hawaii, which is the southernmost island in the Hawaiian archipelago.
• It’s not the tallest (that title goes to Mauna Kea) but it’s the largest and makes up about half of the island’s land mass. Mauna Loa’s volume is estimated to be at least 18,000 cubic miles (75,000 cubic kilometers), making it the world’s largest volcano when measured from the ocean floor to its summit.

3. Volcanic Eruptions

• The deeper one goes under the surface of the Earth towards its core, the hotter it gets. The geothermal gradient, the amount that the Earth’s temperature increases with depth, indicates heat flowing from the Earth’s warm interior to its surface. At a certain depth, the heat is such that it melts rocks and creates ‘magma’.
• Magma is lighter than solid rock and hence it rises, collecting in magma chambers. Chambers that have the potential to cause volcanic eruptions are found at a relatively shallow depth, between six to ten km under the surface. As magma builds up in these chambers, it forces its way up through cracks and fissures in Earth's crust. This is what we call a volcanic eruption. The magma that surfaces on the Earth's crust is referred to as lava

4. Less Explosive volcanoes-Mauna Lao

 Runny magma makes for less explosive volcanic eruptions that typically are less dangerous. Since the magma is runny, gasses can escape, leading to a steady but relatively gentle flow of lava out of the mouth of the volcano. The eruption at Mauna Loa is of this kind. Since the lava flows out at a slow pace, people typically have enough time to move out of the way

5. Explosive Volcanoes

If magma is thick and sticky, it makes it harder for gasses to escape consistently. This leads to a build-up of pressure until a breaking point is reached. At this time, the gasses escape violently, all at once, causing an explosion. Lava blasts into the air, breaking apart into pieces called tephra. These can be extremely dangerous, ranging from the size of tiny particles to massive boulders.

6. Impact of Explosive Volcanoes

• The eruptions can be deadly: as thick clouds of tephra race down the side of the volcano, they destroy everything in their path. Ash erupted into the sky and falls back to Earth like powdery snow.
• Blankets of ash can suffocate plants, animals, and humans.
•  Further, when the hot volcanic materials mix with nearby sources of water, they can create mudflows that have been known to bury entire communities alive. Mount Vesuvius, which obliterated the city of Pompeii, is an example of an explosive volcano.

7. Volcanic Explosivity Index

 The Volcanic Explosivity Index (VEI) is a scale used to measure the explosivity of a volcano. It has a range of 1 to 8 with a higher VEI indicating more explosivity. Mauna Loa has been 2, in the explosivity index

8. Types of Volcanoes

•  Active Volcano-Any volcano that has erupted within the Holocene period (in the last 11,650 years) is considered to be “active” by scientists.
•  Dormant volcanoes-these are those active volcanoes that are not in the process of erupting currently but have the potential to do so in the future. Mauna Loa was a dormant volcano for the last 38 years.
•  Extinct volcanoes are ones that scientists predict will never face any further volcanic activity. Ben Nevis, the tallest mountain in the UK, is an extinct volcano.

9. Famous Volcanoes

Krakatoa, Indonesia

 One of the most catastrophic volcanic eruptions ever occurred in Krakatoa in 1883 (VEI 6). The volcano released huge plumes of steam and ash. The explosions were so brutal; they were heard 3,100km away in Perth, Western Australia. According to the Dutch colonial authorities, Krakatoa’s eruption and the consequent tsunamis caused 36,417 deaths, though modern estimates peg the number to be much higher.

Mount Vesuvius

In 79 CE, Mount Vesuvius erupted (VEI 5), in one of the deadliest eruptions in European history, killing as many as 16,000 and destroying the town of Pompeii. According to scientists, the explosion released 100,000 times the thermal energy that was released with the atomic bombings at Hiroshima and Nagasaki. It is said to have instantly boiled the blood of all those who were too close to it.

Mount Fuji, Japan

Mount Fuji towers over the countryside with its snowcapped peaks and barren surface. It last erupted in 1707-1708 (VEI 5) and had a devastating effect on the local population. The tephra release led to a significant agricultural decline, leading to widespread starvation in the Edo (now Tokyo) area.

Eyjafjallajokull, Iceland

 Iceland Sometimes referred to as E15, it is one of the many volcanic features of Iceland. In 2010, a relatively small eruption (VEI 4) managed to bring air traffic in Europe to a complete standstill. 20 countries closed their airspace, impacting approximately 10 million travelers.

 Kīlauea, Hawaii

 Adjacent to the Mauna Loa, this is one of the most active volcanoes on the planet. It has been erupting intermittently since recorded history, with its eruption lasting from 1983 to 2018 being the longest continuous eruption ever recorded. It is a major tourist attraction, with the earliest hotel built at the edge of the volcano in the 1840s.

 Mount St Helens, USA

Located in Washington State, Mount St. Helens was a major eruption that occurred on May 18, 1980 (VEI 5), and it remains the deadliest and most economically destructive volcanic event in U.S. history. It remains an active volcano and one that is considered to be amongst the riskiest by scientists.

For Prelims & Mains