NEET BIOLOGY

Detailed explanation-1: -Those associated with eruptions are sometimes caused by oversteepening of a volcano’s flank by intrusion of a shallow body of magma within or just beneath the volcanic cone, as happened at Mount St. Helens.

Detailed explanation-2: -Volcanic mudflows (lahars and debris flows) occur more commonly after a landscape has been covered by loose volcanic material. Sign on the slopes of Rabaul, Papua New Guinea. Eruptions may trigger lahars by melting snow and ice or by ejecting water from a crater lake.

Detailed explanation-3: -Lahars transform the landscapes around Cascade Volcanoes. Lahar is an Indonesian word describing a mudflow or debris flow that originates on the slopes of a volcano. Small debris flows are common in the Cascades, where they form during periods of heavy rainfall, rapid snow melt, and by shallow landsliding.

Detailed explanation-4: -Volcanic ash is formed during explosive volcanic eruptions. Explosive eruptions occur when gases dissolved in molten rock (magma) expand and escape violently into the air, and also when water is heated by magma and abruptly flashes into steam. The force of the escaping gas violently shatters solid rocks.

Detailed explanation-5: -Although there are several factors triggering a volcanic eruption, three predominate: the buoyancy of the magma, the pressure from the exsolved gases in the magma and the injection of a new batch of magma into an already filled magma chamber.