Hunga Tonga–Hunga Haʻapai (HTHH) Volcano

About Hunga Tonga–Hunga Haʻapai (HTHH):

• It is a submarine stratovolcano in the Tongan archipelago in the southern Pacific Ocean.
• The HTHH volcano includes the small islands of Hunga Tonga and Hunga Ha’apai, along with shallow reefs along the caldera rim of a much larger submarine edifice in the western South Pacific Ocean, west of the main inhabited islands in the Kingdom of Tonga. 
  • It is located about 30 km south of the submarine volcano of Fonuafoʻou and 65 km north of Tongatapu, the country's main island.
• The volcano is part of the highly active Tonga–Kermadec Islands volcanic arc, a subduction zone extending from New Zealand north-northeast to Fiji.
• The Tonga-Kermadec arc was formed as a result of the subduction ofthe Pacific Plate beneath the Indo-Australian Plate. 
• It has erupted regularly over the past few decades.

What is a Stratovolcano?

• It is a tall, steep, and cone-shaped type of volcano.
• Unlike flat shield volcanoes, they have higher peaks.
• They are typically found above subduction zones, and they are often part of large volcanically active regions, such as the Ring of Fire that frames much of the Pacific Ocean.
• Strato Volcanoes comprise the largest percentage (~60%) of the Earth's individual volcanoes, and most are characterized by eruptions of andesite and dacite, lavas that are cooler and more viscous than basalt.
• These more viscous lavas allow gas pressures to build up to high levels. Therefore, these volcanoes often suffer explosive eruptions. 
• They are usually about half-half lava and pyroclastic material, and the layering of these products gives them their other common name, composite volcanoes.
• At their peak, they usually have a small crater. The crater may be filled with water or ice, or it may contain a volcanic dome during a period of relative inactivity.

Q1: What are Pyroclasts?

Pyroclasts (or "tephra') are any volcanic fragments that were hurled through the air by volcanic activity. A pyroclastic eruption is one in which the great majority of activity involves fountaining or explosions. A pyroclastic deposit is the resulting layer or pile of material that has fallen to the ground by one or many pyroclastic eruptions. A pyroclastic rock is the hardened, solidified, or compressed version of an originally loose pyroclastic deposit.

Source: Tonga’s volcanic eruption could cause unusual weather for the rest of the decade, new study shows