Hazards: Volcanoes
What Are Volcanoes?
A volcano is a landform created by magma from the earth's interior which penetrates through
weaknesses in the Earth’s surface. Most volcanoes are formed at plate boundaries. They can
be classified according their physical state or their type of eruption.
-According their state, volcanoes can be:
-Active: if it’s going through an eruption
-Dormant: if it’s not erupting at the moment, but it’s expected to erupt in future
-Extinct: if it’s not expected to erupt
-There are lots of different types of volcanoes according to their type of eruption, such as the
following examples.
- What Causes Volcanoes to Erupt?
*Review:
-Inner core (solid)
-Outer core (liquid)
-Mantle (plastic)
- Convection: Hot material placed on the outer core starts to rise due to its loss of
density (caused by the increase in temperature). As this material moves apart from the
heat source, heat energy is transferred to surrounding particles. Little by little the
material decreases its temperature and gains density, sinking again and gaining once
more heat that will make it rise, so the process is repeated again and again…
Magma contains a mixture of silicates and dissolved gases. As magma rises closer to
the Earth’s surface the pressure decreases and the dissolved gases come out of
solution to form bubbles. As the bubbles expand the magma is pushed into the
volcanic vent until it breaks through weaknesses in the Earth's crust. The explosive
potential of the volcano is dependent on the effervescence of the gases and the
viscosity of the magma. High gas effervescence and low viscosity cause the most
explosive eruptions.
-Prediction
Scientists can use seismic waves to show if a volcano is getting ready to erupt. Many
volcanoes experience an increasing intensity in frequency and size of earthquakes as
they prepare to erupt. Patterns of seismicity are complex and often difficult to
interpret; however, increasing seismic activity is a good indicator of increasing
eruption risk, especially if long-period events become dominant and episodes of
harmonic tremor appear. We can also use gas emissions. As magma nears the surface
and its pressure decreases, gases escape. This process is much like what happens when
you open a bottle of fizzy drink and carbon dioxide
escapes. Sulphur dioxide is one of the main
components of volcanic gases, and increasing
amounts of it herald the arrival of increasing
amounts of magma near the surface.
Ground deformation. Swelling of the volcano signals
that magma has accumulated near the surface.
Scientists monitoring an active volcano will often
measure the tilt of the slope and track changes in the
rate of swelling. An increased rate of swelling, especially if accompanied by an increase
in Sulphur dioxide emissions and harmonic tremors is a high probability sign of an
impending event.
-3Ps
-Prevention and preparing.
There are dangers that volcanic eruptions pose to people so it is important that they
know how to handle situations before, during and after volcanic eruptions to avoid
serious problems. The government has agencies that take care of reporting
information about a certain volcano and its activities in order for people to be warned
and avoid unpleasant incidents from happening.
Be prepared either to shelter or to evacuate. Develop an evacuation plan and a
sheltering plan for yourself, your family, and others in your household. Review the
plans and make sure that everyone understands them. You need to have these things:
flashlight and extra batteries, first aid kit and manual, emergency food and water,
manual (nonelectric) can opener, essential medicines, respiratory (breathing)
protection, eye protection (goggles), battery-powered radio.
Follow authorities’ instructions if they tell you to leave the area. Though it may seem
safe to stay at home and wait out an eruption, doing so could be very dangerous.
Volcanoes spew hot, dangerous gases, ash, lava, and rock that are powerfully
destructive.
-Preparedness evacuation plan for El Hierro
El Hierro is at a volcanic risk area. The whole island is at yellow risk, except the area of La
Restinga (which is at red risk).
The plan is the following:
-Yellow alert (Pre-emergency): Pay attention to the communications of the civil protection.
Classification:
-Strong: Several relevant parameters present anomalies with respect to the mean with
an indication of a possible pre-eruptive state
-Intense: The indicators are coherent with a pre-eruptive state
-Red alert (Maximum alert) - red implies the beginning of a preventive evacuation. Be at
authorities’ disposal). Classification:
1) Pre-eruptive phenomena: The situation will not probably return to normality
2) The eruption begins
Alarm: The volcanic activity is extremely violent, the
emergency services are overflown
and/or an overcome forecast
-Protocol: Vigilance System-Scientific team-Forecast-Civil Protection
-Prevention:
-Laws
-Education
-Protection
If a lahar, pyroclastic flow, or lava flow is headed toward you, leave the area immediately. If
you are warned to evacuate because an eruption is imminent, evacuate.
If you can drive rather than walk, use your vehicle to evacuate. When driving keep doors and
windows closed, drive across the path of danger if you can or away from the danger if you
cannot, and watch for unusual hazards in the road.
If you are indoors
Close all windows, doors, and fireplace or woodstove dampers. Turn off all fans and heating
and air conditioning systems. Bring pets and livestock into closed shelters.
If you are outdoors
Seek shelter indoors. If caught in a rock fall, roll into a ball to protect your head. If near a
stream or river, be aware of rising water and possible mudflows in low-lying areas. Move upslope as quickly as possible. Seek care for burns right away. Immediate care can be lifesaving.
If your eyes, nose, and throat become irritated from volcanic gases and fumes, move away
from the area immediately. Your symptoms should go away when you are no longer in contact
with the gases or fumes. If the symptoms continue, consult your doctor.
Protecting yourself during ash fall
Stay inside, if possible, with windows and doors closed.
Wear long-sleeved shirts and long pants.
Technology offers as an instantaneous connection with the rest of the world. During the last
years several apps that tell us about meteorology and hazard’s alert have been released.