Chapter 8 Flashcards

Question

What happened with the eruption (facts plis)

Answer 1

About 1600 BC the Santorini volcano erupted 60 km3 of pyroclastic material (second largest ever) (the largest was 100 km3 from Mount Tambora in Indonesia in 1815) the roof and rim of the volcano magma chamber caved in, creating what’s called a collapsed caldera, letting in the sea, and the resultant explosion set of a tsunami through the Aegean Sea This destroyed the Minoan civilization because everything they had was either in the shipping lines or in the harbours around the region – and that was destroyed. Not long afterward, the Mycenaean warriors arrived on the scene and readily defeated the last of the Minoans

Answer 2

About 350 BC, Plato wrote a couple of stories in which he described a wonderful city called Atlantis that suddenly sank into the sea one day One stumbling block has always been that Plato said Atlantis was “beyond the Pillars of Hercules”, which was Gibraltar, placing the lost city in the Atlantic Ocean. So it appears that Atlantis is modeled after Santorini

Answer 3

5 February AD 62, an earthquake jolted what is now Naples Many buildings in Pompeii were destroyed For the next 16 years, small earthquakes struck the area, but were not associated with the volcano The story was recorded by Pliny the Younger, with help from the records of his father, Pliny the Elder

Answer 4

At about 1 pm on 24 August 79 AD, from their vantage point across the Bay of Naples at Misenum, the Pliny family noted a curious large cloud developing above Mount Vesuvius It was for the meticulousness of his descriptions that this phase of an eruption is called a Plinian eruption The Elder sailed to Stabiae to pick up some people, found them extremely frightened and, to calm them, had them organize a great meal and get the baths going. the Younger stayed back Back in Misenum, The Younger kept a record of waht happened (the ash, eruption, **darkness**, etc)

Answer 5

Herculaneum was the first to be destroyed, by lahars (20 m deep) The lack of remains indicates that people must have evacuated (but still died at the beach) It was buried in a matter of minutes Only some 40,000 m2 of Herculaneum has ever been excavated; in time, another town (Ercolano) was built on top of the buried one

Answer 6

Pompeii was 9 km downwind from the volcano It was buried very quickly under 3 m of ash no one ever attempted to dig anything out, to recover anything or any bodies in 1595 a few coins and fragments of a marble tablet were dug up at an excavation site for a new aqueduct, baering the name Pompeii Instead of preserving the treasures below they were pillaged by wealthy collectors, such as the British ambassador to Naples Gradually, in the 19th Century, more order was maintained, and, although too late for almost the whole city, some parts were studied properly

Answer 7

Vesuvius continued to blow. It apparently blew about 650 BC, 79AD, 203, 472, 512, 685, 993, 1036, 1049, 1138; it waited until 1631 to awake again, destroying 6 towns. The final gasps of that sequence seem to have been about the 1890s should the volcano reactivate again, several hundreds of thousands live too close

Answer 8

A region that consists of a number of volcanic rings and cones within a 13 km diameter crater Known eruption times in the ancient past are: 47,000 years ago, 36,000, 15,000- 9500, 8600-8200 and 4800-3800 histrorical eruptions: 1158 and 1538 Naples sits on the old crater floor, where you can see the ridges of a major Plinian eruption (4400 years ago)

Answer 9

They can form anywhere (they are deep beneath the crust) The cores may be about 300°C hotter than surrounding rocks, but the edges are only some 100°C or so hotter than the background temperature. Even that relatively small difference is enough to reduce viscosity and initiate magma flow

Answer 10

- mantle plume - very benign

Answer 11

Some 75 million years ago the first eruptions took place over that plume The first island gradually built up from the sea floor. As the surface approached sea level – but was still below – it was called a seamount Over time, as the Pacific Plate drifted over the mantle plume, a string of volcanic islands was formed

Answer 12

About 43 million years ago, the direction of drift of the Pacific Plate changed reflected by a ‘dog’s leg’ pattern change in the string of islands n fact, the earliest volcanic islands formed (named the Emperor Islands) are now starting down the subduction zone to the north called the Aleutian Trench

Answer 13

Having moved off the mantle plume, the volcanoes lost their magma feed and began to weather and erode away. As they fell below sea level, they again were called seamounts.

Answer 14

In the beginning, it is pure basalt Over time, assimilation happens and the lava cahnges in composition Now, the composition of magma erupting at Kilauea is not equivalent to MORB – it’s more properly called alkali basalt to reflect the small modification in composition.

Answer 15

magma rises from the hotspot on the top of the plume into a shallow magma chamber at about 3-6 km depth, then rises from there along individual vents or fissures to surface Small earthquakes will also occur as a result

Answer 16

there are only one or two rare cases where people were killed by an eruption in Hawaii. In 1790, as members of King Keoua's army were traveling past Kilauea, a sudden eruption of gases developed into something called a 'ground surge', in which a hurricane-like wind carried the hot gasses directly from the vents through the adjacent valley.

Answer 17

Like with one under an ocean (Hawaii) they constantly spew lava. With continental calderas, the lava gets stored and builds up That goes on for the life of the mantle heat plume – which we already know is 100 million years or maybe even 200 million years.

Answer 18

It must break through the crust, assimilating, which increases explosion risk, just like with subduction zone volcanoes

Answer 19

Once a mantle heat plume is established and viscous rhyolitic magma forms in the hotspot The land bulges At some point the upward pressure of that magma becomes greater than the confining pressure of the surrounding rocks A plinean eruption occurs

Answer 20

Rhyolitic (with inital explosion) middle-chamber less-modified andesitic magma follows only unmodified basalt concludes the eruption stages

Answer 21

Volcanic rocks first appeared from this plume/hotspot about 17 million years ago in the northeastern part of Nevada North American plate migrated to the southwest over the stationary plume The caldera dated more recently than 11 mya

Answer 22

the broad, rather featureless arcuate depression that extends across southern Idaho is the Snake River Plain started at about 11 mya and finishing about 700,000 years agp

Answer 23

After the magma chamber has been emptied, there’s a channel open for partial melt magma of basalt composition to come roaring straight up through the existing plumbing

Answer 24

it started as the bulk of the Farallon plate was subducted under California and the transform San Andreas came into being. during the time of the Farallon subduction, the western edge of the North American plate was under compression – thus it shortened by building great mountain ridges inland but more or less parallel to the coast. The land has been "relaxing" allowing great extension of the lithosphere in a so-called ‘basin and range’ type of structure

Answer 25

way back at Yellowstone, the motion is really slow: about 4.5 mm per year (slower than it used to be)

Answer 26

Right now the site of Yellowstone is - by far - the largest heat flow anomaly in the US Three enormous eruptions have occurred at Yellowstone * 2 million years ago (volume erupted: 2200 17 km3) * 1.3 million years ago (volume erupted: 280 km3) * 600,000 years ago (volume erupted: 1000 km3)

Answer 27

explosive period as about once every 650,000 years

Answer 28

There’s no signal that activity at Yellowstone is abating. The last eruption threw tephra as far as present-day Louisiana

Answer 29

in the last 600,000 years the volcano has erupted another 1000 km3 in dribs and drabs, equaling the amount discharged during the 3rd major eruption During the past 150,000 years, extensive flows of rhyolite have buried much of the Yellowstone basin The youngest lavas erupted in the park only about 70,000 years ago a large reservoir of hot magma again exists at shallow depth beneath the park

Answer 30

Judging by the last three eruptive cycles, it took from about 200,000 to 600,000 years to generate the magmas needed for an ash flow holocaust.

Answer 31

We can't tell whether rhyolite eruptions of the last 150,000 years represent the end of the third caldera-forming cycle or a significant precursor of the fourth Evidence suggests that Yellowstone's thermal frequent earthquakes suggest that fresh magma has been injected into Yellowstone's magma reservoir since the last eruption

Answer 32

seismic evidence shows there to be a very large body of rhyolitic magma sitting some 5-10 km under Old Faithful 35 years ago, you could comfortably walk over the ground. Now, it is too hot

Answer 33

First, there will be a series of small to moderate eruptions the Yellowstone volcano will eventually stage another caldera-forming cataclysmic eruption that could reduce large areas of western North America to a rhyolite desert This will be the most catastrophic event humans have ever witnessed much of the USA would be wiped out (most people, most industry, most agriculture) by lava flows and pyroclastics, affecting the rest of the world as well.

Chapter 8 Flashcards

(57 cards)