Krakatau (1)

(1)

Krakatau

(2)

Misc Stuff

• _{1NM = 1.852km}

• _{Speed of sound at sea level = 1225km/hr}

• _{Earth’s radius 6,372 km}

(3)

(4)

Speed of the Tsunami

• _{The paroxysmal explosion and collapse of the}

volcano of Krakatoa generated formidable tsunami

waves that were up to 37 m (120 feet) in height.

These waves destroyed 295 towns and villages in

the Sunda Strait in Western Java and Southern

Sumatra. A total of 36,417 people were drowned.

The tsunami, being of volcanic origin (a point

source) was only destructive locally in Indonesia.

However, small tsunami waves were recorded

(5)

(6)

Undoubtedly, the atmospheric pressure waves from the three gigantic eruptions of Krakatoa on August 26 and 27, 1883, which proceeded the fourth paroxysmal

explosion, gave rise to tsunami like waves. The first of these three proceeding violent explosions occurred at 17: 07 Greenwich time (GMT) on August 26, 1883. The second and third violent eruptions occurred at 05:30 GMT and at 06:44 GMT on August 27, 1883. Being of atmospheric origin and small in size, none of these earlier tsunami like waves were noticed or reported. At the time, the only

operating tide gauge in Batavia (Jakarta) was too far away to record these smaller sea level oscillations.

It was the fourth paroxysmal explosion of Krakatoa at 10:02 (GMT) that gave rise to the gigantic destructive tsunami waves in the Sunda Strait. This paroxysmal

explosion blew away the northern two-thirds of the island and it was almost instantaneously followed by the collapse of the unsupported volcanic chambers which formed the huge underwater caldera. It was the combined effects of the explosion and collapse of the volcano that generated the catastrophic tsunami waves that caused havoc and destruction in the Sunda Strait.

(7)

Task 1.

Determine the speed of the Aden wave

from Krakatau.

• Given the speed of sound (1225 km/hr) and the

distance from Krakatau to Aden, Yemen (3,800

(8)

Speed of the explosive sound

• _{In 1883, the eruption of the Indonesian volcano}

Krakatoa was heard at Rodriguez Island and it

remains the furthest point at which the explosion

was heard. The sound was described as "the roar of

heavy guns". Naval ships were ordered to

(9)

Task 2

The time the eruption was heard on Rodriguez

• _{First, calculate the time it would take the noise}

to reach Rodriguez.

• _{Second, assume that the second and third}

blasts were the loud noises heard on

(10)

Dust and Ash Cloud

• _{Tephra from the eruption fell as far as 2,500}

km downwind in the days following the

eruption. However, the finest fragments were

propelled high into the stratosphere,

spreading outward as a broad cloud across the

entire equatorial belt in ~ 13 days. These

particles would remain suspended in the

(11)

(12)

• _{The stratospheric cloud of dust also contained large}

volumes of sulfur dioxide gas emitted from Krakatau.

These gas molecules rapidly combined with water vapor to

generate sulfuric acid droplets in the high atmosphere.

The resulting veil of acidic areosols and volcanic dust

provided an atmospheric shield capable of reflected

enough sunlight to cause global temperatures to drop by

several degrees. This aerosol-rich veil also generated

spectacular optical effects over 70% of the earth's surface.

For several years after the 1883 eruption, the earth

experienced exotic colors in the sky, halos around the sun

and moon, and a spectacular array of anomalous sunsets

and sunrises. Artists were fascinated by these aerial

displays and captured them on canvas. The painting shown

here is one such sunset captured by the artitst William

(13)

Sunsets after the

eruption painted on

26 November 1883 at

Chelsea (London)

England. Painted at

~4:40 (top), 5:00

(mid), & 6:00

(14)

Task 3

Speed of the Stratospheric Dust Cloud.

• _{First, find the circumference of the base of the}

stratosphere in km. Assume:

–

_{Earth’s radius 6,372 km}

–

_{the stratosphere is 12 km above the surface of the earth}

–

_{C = 2πr}

• _{Second, convert the days it took the dust to}

circumnavigate the Earth (13 days) to hours.

• _{Third, determine the speed at which the}

(15)

Affect on Climate

• _{The dust clouds from large eruptions shade}

the planet and reflect solar energy back out to

space. This can decrease the global

(16)

Example:

The Tambora Eruption of 1815

• _{Tambora 1815}

• The 1815 eruption of Tambora was probably the largest eruption in historic

time. About 150 cubic kilometres of ash were erupted. This is about 150

times more than the 1980 eruption of Mount St. Helens in USA. Ash fell as

far as 1,300 km from the volcano. In central Java and Kalimantan, 900 km

from the eruption, one centimetre of ash fell. The eruption column is

estimated to have reached a height of about 45 km.

(17)

Task 4

• _{Based on the graph of surface air temperatures}

in England answer the following questions.

1. Highlight the temperature changes caused by

the Tambora and Krakatau eruptions.

2. Based on your analysis estimate relatively how

much ash Tambora injected in to the

(18)

(19)

Task 5

• _{Draw a bar graph showing the speeds of the}

tsunami, atmospheric concussion, and the

stratospheric dust. Graph them in this order.

• _{Calculate the ratio of each speed relative to}

the speed of sound at sea level (1225km/hr)

• _{Compare the three speeds in complete}

sentences.