What kind of magma does vesuvius have

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Plaster casts: Victims of the 79 A. Ruins at the ancient city of Pompeii Brick columns stand among ruins of the ancient city of Pompeii. Did You Know? The 79 AD eruption of Vesuvius is why volcanologists use "Plinian" to describe large volcanic eruption clouds. Pliny the Younger, a Roman historian who witnessed the 79 AD eruption, wrote the oldest surviving description of the tall, tree-shaped cloud that rose above the volcano. Modern volcanologists use the term to describe large-volume, violent eruptions that produce quickly-expanding clouds of rock, ash and gases which rise many miles into the atmosphere.

Some more recent examples of Plinian eruptions include Mount St. Helens in and Pinatubo in Here is Pliny's description Its general appearance can be best expressed as being like an umbrella pine, for it rose to a great height on a sort of trunk and then split off into branches, I imagine because it was thrust upwards by the first blast and then left unsupported as the pressure subsided, or else it was borne down by its own weight so that it spread out and gradually dispersed.

Sometimes it looked white, sometimes blotched and dirty, according to the amount of soil and ashes it carried with it. Gates, A. Wortel, M. Review full text upon subscription. Spatter Cones Mount St. Find Other Topics on Geology. Maps Volcanoes World Maps. Facts About Mount Vesuvius. In B.

The area was frequently jolted by large earthquakes. This decorative stonework records the damage caused by an earlier earthquake, perhaps the earthquake of 62 A. Copyrighted photograph of Robert Decker. The 79 A. From 18 miles 30 km west of the volcano, Pliny the Younger, witnessed the eruption and later recorded his observations in two letters. He described the earthquakes before the eruption, the eruption column, air fall, the effects of the eruption on people, pyroclastic flows, and even tsunami.

Volcanologists now use the term "plinian" to refer to sustained explosive eruptions which generate high-altitude eruption columns and blanket large areas with ash. It is estimated that at times during the eruption the column of ash was 20 miles 32 km tall. About 1 cubic mile 4 cubic kilometers of ash was erupted in about 19 hours. Volcanoes by Peter Francis contains several direct passages from Pliny the Younger and describes the archeology of Pompeii and Herculaneum.

Copyrighted photograph of a street in Pompeii by Robert Decker, Vesuvius is in the background. About 10 feet 3 m of tephra fell on Pompeii, burying everything except the roofs of some buildings. The city was abandoned and its location forgotten. In , excavations discovered artifacts at Pompeii and centuries of pillaging followed. Archeological excavations began in the mid-nineteenth century. Now, much of Pompeii has been excavated and it has revealed much about how people lived during that time and died during the eruption.

There are numerous molds of people in their final moments. The mold of a dog is shown in the above photo. The poor animal was chained to a post and struggled for hours before finally succumbing to the ash. Herculaneum was buried under 75 feet 23 m of ash deposited by a pyroclastic flow. Because upwelling convection currents moving through the lithospheric gap can interact with the enriched mantle from the subducting slab, lithologies unique to Mount Vesuvius are different from the rest of the Arc.

Subduction of varying velocities along the length of the subduction zone typically causes plates to tear. The slab window beneath Mount Vesuvius is bounded by two faults that were torn along the margin due to stresses caused by these changes in velocity. These slab tear faults probably connect two adjacent sections of the subduction zone, and accommodate horizontal movements if the two sections move at different velocities. Upwelling convection currents worked in conjunction with varying subduction velocities, and this is believed to have caused the detachment and tear, creating the slab window.

The many chemical compositions of the resulting rocks do not show a clear trend in contrast to typical volcanic products, which have compositions that can simply be explained by fractional crystallization. Analysis of geochemical data from a borehole drilled to a depth of m along the southern slopes of Mount Vesuvius through rock layers known as the CdT sequence has provided insight into the causes of compositional variation.

Borehole evidence shows that three different processes cause the variations in rock types: heterogeneous source composition, magma mixing, and crustal contamination. Mantle xenoliths that are brought to the surface in ascending magma bodies are evidence of the chemical alterations beneath Mount Vesuvius. Strontium isotope analyses have been used to determine the sources of contamination and the varying degrees of differentiation.

Because radiogenic Strontium ratios were not consistent within the magmas, magma mixing has sourced variations in rock type. Mount Vesuvius is well known for its 79 CE eruption, which buried the cities of Pompeii and Herculaneum. Mount Vesuvius has erupted several times since 79 CE, and beginning in , Mount Vesuvius entered a long period of frequent volcanic activity continuing until The eruption, the largest eruption since 79 CE, destroyed neighboring cities with pyroclastic flows.

In March of , Vesuvius sustained a plinian eruption, destroying many aircrafts involved in World War II; however, no one was killed or injured during this eruption. Lassen Peak is the southernmost active volcano in the Cascade Arc, a volcanic arc along the western United States that has been slowly migrating northwest due to North American plate movement.

The complex interrelated tectonic forces associated with each of the aforementioned plates and their associated orogenic events are unique to Lassen Peak, and are significant because they have contributed to its volcanic activity and characteristic lithology.

In contrast to the majority of volcanism in the Cascade Arc, which is predominantly calc- alkaline in nature, volcanism of the southern Arc is compositionally diverse. Larger and longer-lived lithologically complex volcanic centers are interspersed among these regional volcanoes and produce rocks of varying composition ranging from mafic and felsic andesite to felsic dacite and rhyolite.

Lassen Peak belongs to the latest of these stages, which has produced intermediate andesites alongside domes of dacite and rhyodacite. Even though Lassen Peak and Mount Vesuvius have both experienced magmatic evolution throughout their active lives, the processes that spurred the evolution are not exactly the same, and therefore each volcano has its own lithological composition.

Lassen Peak has had two primary eruptive periods in its lifetime. Beginning on May 30, , volcanic activity commenced at Lassen Peak through numerous steam blasts and increased hydrothermal activity. On May 14, , a lava dome of black dacite with andesitic inclusions began to accumulate.