Volcano tam 2013-02

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VOLCANIC ERUPTIONS AND ITS EFFECTS ON

CROP PRODUCTIONS

VOLCANIC ERUPTIONS:It is a natural geological hazard.

Volcanoes occur at tectonic plate boundaries and at hot spots, where molten rock , or magma, forms and rises to the surface.

Most of the volcanoes are located at or near tectonic plate boundaries.

The temperature, pressure, and fluid content of rock play roles in the formation of magma.

Classification of volcanoes

The processes and deposits dictate the morphology of volcanoes.

Three types of volcano:

Volcanoes are classified according to their morphology.

Cinder Cone Volcanoes• A cinder cone volcano is a

relatively small, volcano with steep sides. It is where rock and ash shoot up into the air and fall back around the opening.

• Materials Erupted: small pieces of hardened lava (rock fragments) - called cinders– Moderately explosive

• Example: Paricutin (Mexico) .

Volcanoes that alternate between periods of lava flows (constructive phase) and periods of explosive eruptions (destructive phase).

Commonly called “composite volcanoes” because they are made up of both lava and pyroclastic deposits.

Steep slopes, at angle of repose or greater.

Stratovolcanoes

© Noemi Emmelheinz 2001

Shield volcanoes: dominated by lava flows

• Dominated by fluid, high temperature,

low viscosity basaltic magma.

• A shield volcano is broad with gently

sloping sides and has quiet eruptions

like those in Hawaii

• Basaltic lava can also flow through

large cracks called fissures.

• Under water flood basalts are

responsible for creating much of the

new seafloor

Volcanic Hazards

Damage limited to the vicinity in the immediate area of the volcano.

Lava flows

Commonly destroy property in Hawaii and Iceland.

Fatalities rare due to slow speed of advancing lava flow.

Different types of lava

Aa type of lava Pahoehoe:

Pillow lavaBlocky lava

Ash fall

Extensive property damage and fatalities can result from heavy ash falls.

Significant ash in the upper atmosphere can circle the globe in a matter of weeks.

More than 80 commercial jets have been damaged by flying through volcanic ash clouds.

An ashfall 10 million years ago killed these rhinos that are preserved at Ashfall Fossil Beds State Historic Park, Nebraska.

Ash fall and its effect on crops

Plantation forestry on the slopes of Mt Etna during the 2002 eruption, unaffected by several millimetres of fallen ash;

Acid rain damage to coffee plantation

The high sulphur concentration adhered to the ash may induce copper and

cobalt deficiencies in the long term. Ash falls greater than 10-15 cm (4-6 in) typically result in the complete

burial of pastures and soil. the soil will become sterile

Periods when crops are most at risk Pea : from emergence until end of flowering. Squash : during the initial stages of growth and flowering. Tomatoes : during seed emergence and flowering stages. Sweetcorn : during the early stages of growth The most critical period for corn yields is between three weeks before

tasselling to two weeks after pollination. Even light ash falls during this period could result in barren stalks and crop failure

Mitigation measuresO Remove ash from leaves.O Where ash falls have been around 5-25

mm, clear ash from the base of trees to prevent plant disease or death from crown rots fostered by the contact of damp ash with the trunk

O Mix thinner layers of ash into the topsoil.O Where plants have been partially

defoliated, fruit should be thinned . Applying fertilizer will also promote the growth of new leafs

Red Hot Pyroclastic Cloud with LightningChile, South America

Lahars can be the most devastating outcome of many volcanoes.Water and debris rushed down the slopes, picking up more debris along the way.

The lahar killed 28,700 people and destroyed over 5,000 structures in the Amero

A 5 metre wall of water and debris slammed into the town of Amero, 72 km from the volcano

LandslidesLandslides can be generated when a volcano collapses during an eruption.

During the Mt. St. Helens eruption 2.3 km3 of debris slid down the mountain at speeds up to 240 km/hr.

The slide traveled over 24 km and left a 45 m deep deposit.

350,000 years ago Mt. Shasta experienced a similar eruption and landslide that was 20 times greater than that of Mt. St. Helens.

Gas emissions

Lake Nyos 10 days after the 1986 eruption

Gas concentrations in the soil in some areas near the mountain are high enough to kill trees and small animals.

Approximately 260,000 people have been killed by volcanoes in historic times…most by a handful of individual eruptions.

Prediction of Volcanic Eruptions

Identify volcanoes and the frequency and style of their eruptions (a geological problem).

Long Term Prediction

Establish the level of risk based on historic and geologic record.

Preparing hazard maps

VDAP is the only rapid-response volcano crisis team in the world

Short-term prediction

Gas emissions: rates of emission and type of gas changes in some volcanoes

Earthquakes: generated as the magma moves up

Seismicity and geochemistry are two of the technics for monitoring active volcanoes

Surface tilting: recognition of changes in the land surface due to building pressure in the conduit.

A surface bulge appeared on Mt. St. Helens prior to its eruption.

April 26 May 2

April 8, 1980

A combination of approaches is likely the key to short-term prediction.

Recent volcanic eruption in world Barren Island – Active Volcano in India

The only active volcano in India is located in Barren Island. The volcano erupted twice in recent past, once in 1991 and again in 1994-95,

Bárdarbunga During 27 August 2014

M. Jyostna KiranmaiTAM-2013-02Dept. of Agronomy