MAGMATIC PHENOMENA

TURKEY – JUNE 2014

PROJECT FROM ITALY

MAGMA - DEFINITION

• It’s a complex and heterogenous molten rock system

• The physical state is prevalently liquid

• It contains gases (water vopour, carbon dioxide, hydrogen)

• It’s composed by a large number of minerals, mainly silicates

• It’s formed inside the litosphere, at a depht between 50km to 250-500km

• From the solidification of magma, magmatic and igneous rocks are formed

• When magma comes out on the surface and totally or partially loses the gasses present within it, it turns in lava

• It’ classified on the basis of the quantity of silica or silica dioxide present in it

• On the basis of the percentage of silica, four basic types of magma can be listed:

1. Acid Magmas2. Neutral Magmas3. Malfic Magmas4. Ultramalfic Magmas

Parameters ACID MALFIC

% SiO2 SiO2 >= 52% SiO2 <= 52%

Preavailg metals Si, Al Fe, Mg

Fluidity Minimum Maxim

viscosity Maxim Minimum

density 2,7 – 3,0 g/cm3 3,0 – 3,3 g/cm3

Color Lighter Darker

PLUTONISM• It’s a magmatic phenomenon

• It consists in a slow solidification of magma deep in the lithosphere

• Typical of acid magmas, viscous and not very hot

• The gathering of these underground rocky masses is called pluton. It is not visible from the earth surface until a geological phenomenon opens a tectonic window

• Often close to plutons there are veins of precious metals

• Formation of intrusive magmatic rocks formed by large perfect crystals

VOLCANISMIt is a magmatic phenomenon that occors when magma solidifies on the terrestrial surface.

Volcanism’s result is the volcano.

CRATER

SECONDARY CRATER

SECONDARY CONDUIT

CONDUIT

TERRESTRIAL

SURFACE

MAGMATIC CHAMBER

TYPES OF VOLCANO• The eruptive activity of a volcano (and many other

characteristics such as its dimensions, its form...) is determined by the characteristics of its magma.

• These characteristics are its temperature and its chemical composition (concentration of H2O and silicates).

• It's possible to classify volcanoes in 2 big groups: Explosive and Effusive Volcanoes according to their eruptive modality, that is according to the type of erupted magma Types of volcano Parameters

 Explosive volcanoes

 Effusive volcanoes

 1) Type of magma:

 Acid

 Basic

 2) Viscosity of magma.

 High viscosity (higher concentration of silicates)

 Lower viscosity (lower concentration of silicates)

 3) temperature of magma

 Lower (600° - 900°C):

 higher (1000° - 1300°C).

 4) Place of formation of magma:

 Superficial lithosphere.

 Deeper part of lithosphere.

 5) Solidification 

 Faster and earlier (it tends to form “plugs” in the volcanic conduit)  

 Slower and later.

 6) Kind of eruption:

 -Explosive and violent (the plugs in the volcanic conduit cause the formation of deposits of gas and magma which generate strong pressure) - Often it causes fragments and pyroclastic outflows - Often it is followed by earthquakes and landslides. 

 - Effusive and less violent (the gases and magma can easily be discharged, without causing deposits and strong pressure)

 7) Frequency of eruptions: 

 Sporadic, short periods of intense activity alternate with long periods of inactivity. 

 Generally more frequent.

 8) Duration of eruptions:

 Relatively shorter and more intense.

  Longer and continuative.

VESUVIOCharacterictics of volcanoes with esplosive eruptionEsplosive volcanoes generally emits andesitic lava, viscous enough not to form streams of lavaIt forms dome shaped peaks of accumulated lava on the eruption mouthWhen the mass of lava accumulated collapses, an eruptive column of gasses, ash and lapilli erects over the volcanoThey are mainly located where the continental plaques collides with each otherDuring the eruption they can destroy themselves forming a volcanic caldera Important eruption of the Vesuvio79 DC - A very violent explosive eruption took place. That caused the collapse of one of the mountain's sides where the current crater is located. The stream of lava destroyed the Roman city's of Pompei and Ercolano.The last eruption took place in 1944, since then the volcano has been quiet

ETNADefinition• The magma is basic and the lava is fluid and basaltic, the eruption

is of the Hawaiian type. • Behavior effusive and rarely explosive due to abundant gas

emissions of steam. • It is a shield volcano, it has moderately steep sides, the crater is characterized by low slope cones. • Erupts at times fairly close together, initially with a degassing

phenomena and emissions of volcanic sand, followed by the emission of lava.

Famous eruptions 1669 → It was the Etna’s most destructive eruption. It destroyed most of the city of Catania and it created more than 1km of new land. It lasted 122 days and emitted 950 million m3 of lava. 1991 → It was the longest eruption of the twentieth century. And it lasted 473 days

EFFUSION MAGMATIC ROCKS

• Typof magmatic and igneous rocks

• They solidify on top of the earth’s crust with a rapid drop in pressure and temperature

• Amorphous crystalsmcalled Phenocrysts are formed

INTRUSIVE MAGMATIC ROCKS

Definition

• Type of magmatic rocks

• The consolidation take place in depth with a slow diminuition of pressure and temperature

• Big and pure crystals are formed; they've a perfect structure called holocrystalline

GRANITO GABBRO

LIQUID SECONDARY MAGMATIC PHENOMENA

GEYSER• In the subsoil permeable rocks (which form the water conduits) are

surrounded by waterproof rocks. A pocket of magma is close to it, the trapped water, despite the high temperature, can't evaporate because of the pressure caused by the rocks.

• There are two types of geysers: conical geysers (which erupt from a silicon made cone) and fountain geysers (erupting from a lagoon).

• Eruptions take place after a sequence of events:

• The water conduits fill up with water from the outside and from the aquifers, the higher the pressure the greater the force with which the water erupts.

• The heat from the magmatic chamber increases the temperature and the pressure of the water.

• The eruption starts when the water starts to boil, the pressure forces upwards water and vapor and dissipates very quickly.

• A mew eruptive event starts when the water conduits fill up again.

• In Italy there are some small geysers in lake Naftia (Sicily), Fiumicino (near Rome) and in the Valle del Diavolo ( Tuscany).

LIQUID SECONDARY MAGMATIC PHENOMENA

SPRINGS• Hot water sources rich in mineral salts.

• Rain water penetrates in the soil.

• Penetrating deep in the ground the water gets filtered and purified, different types of salts and gasses dissolve depending on the type of rocks.

• The deeper the water is the more pure it becomes

• When the water meets a waterproof layer it forms an aquifer.

• These aquifers heat up and rise to the surface.

• These waters are rich in mineral salts and are used for therapeutic treatments.

• An example in Italy is Abano spirngs

THE END