Fact File; Popocatapetl

Well... it's at it again... so... seeing as I haven't done a fact file on this volcano yet... and now the fact is that it is erupting again makes me think that its about time that I do one.. so... back to my favorite topics... Volcanoes! :)

Fact File; Popocatepetl

 Location;   Popocatepetl is 70 km (43 mi) southeast of Mexico City,
Magma Type- Predominantly Andesitic, but it has also erupted large volumes of Dacite.                                                     Magma produced in the current cycle of activity tends to be a mixture of the two.
Typical eruption style: Dominantly explosive, construction of lava domes. Plinian eruptions at intervals of several centuries or few thousands of years, vulcanian and strombolian activity in intermittent phases.

General Background;  Popocatépetl, whose name is the Aztec word for smoking mountain, towers to 5426 m 70 km SE of Mexico City to form North America's 2nd-highest volcano. The glacier-clad stratovolcano contains a steep-walled, 250-450 m deep crater. The generally symmetrical volcano is modified by the sharp-peaked Ventorrillo on the NW, a remnant of an earlier volcano.
At least three previous major cones were destroyed by gravitational failure during the Pleistocene, producing massive debris-avalanche deposits covering broad areas south of the volcano. The modern volcano was constructed to the south of the late-Pleistocene to Holocene El Fraile cone. Three major plinian eruptions, the most recent of which took place about 800 AD, have occurred from Popocatépetl since the mid Holocene, accompanied by pyroclastic flows and voluminous lahars that swept basins below the volcano. Frequent historical eruptions, first recorded in Aztec codices, have occurred since pre-Columbian time.

This 2003 photo from the International Space Station shows a pair of volcanoes in Mexico. As part of the “Ring of Fire” stretching around the Pacific, Mexico hosts several of the world’s most continually active volcanoes, including the massive Popocatepetl (Aztec for "Smoking Mountain") at left. The neighbouring volcano is Iztaccíhuatl (the "Woman in White"). The faint plume emanating from Popocatepetl’s summit crater shows the ever-present hazard the volcano represents to the 25 million people living in the region, including the nearby city of Amecameca, as well as the metropolitan centres of Mexico City to the northwest and Puebla to the east. Credit: NASA

Nevado del Ruiz... Its Back

Volcano Name- Nevado del Ruiz

Volcano Type- strata volcano

location- colombia

• The Colombian volcano Nevado del Ruiz is an active  stratovolcano with a history of generating deadly volcanic mudflows lahars- from relatively small-volume eruptions.
• In 1595, a lahar swept down the valleys of the River Guali and the River Lagunillas, killing 636 people.
•  In 1845, an immense lahar flooded the upper valley of the River Lagunillas, killing over 1000 people.
• It continued for 70 kilometers downstream before spreading across a plain in the lower valley floor.
• The young village of Armero was built directly on top of the 1845 mudflow deposit.
•  Over the ensuing years, Armero grew into a vibrant town with over 27,000 residents.
• On November 13, 1985, history repeated itself for the third time in 400 years, with another eruption and another deadly lahar racing down the River Lagunillas.
•  This time, over 23,000 people were killed, including most of the residents of Armero. With proper planning, this tragedy could have been averted.
• over the last week the volcano has rumbeld back into life as can be seen on the web-Cams on the BBC page : http://www.bbc.co.uk/programmes/p00tmqd6/features/webcams 
• what could this mean for the people who live below the volcano?.. it remains to be seen... however hopefully due to the increase in knowlage of the volcano and increased monitoring the effects will be mitigated and the damages decreased!

Volcano Fact File; Niriagongo

Volcano name- Niriagongo

Volcano type- Strato Volcano

volcano location- DRC

• Mount Nyiragongo is a stratovolcano in the Virunga Mountains associated with the Albertine Rift.

• It is located inside Virunga National Park, in the Democratic Republic of the Congo, about 20 km north of the town of Goma and Lake Kivu and just west of the border with Rwanda.

• The main crater is about two km wide and usually contains a lava lake. The crater presently has two distinct cooled lava benches within the crater walls - one at about 3175m (10,400 ft) and a lower one at about 2975 m (9800 ft).

• Nyiragongo's lava lake has at times been the most voluminous known lava lake in recent history. The depth of the lava lake varies considerably.

• A maximum elevation of the lava lake was recorded at about 3250 m (10,700 ft) prior to the January 1977 eruption - a lake depth of about 600 m (2000 ft).

• A recent very low elevation of the lava lake was recorded at about 2700 m (8800 ft).

• Nyiragongo and nearby Nyamuragira are together responsible for 40% of Africa's historical eruptions

• Not much is known about how long the volcano has been erupting, but since 1882, it has erupted at least 34 times, including many periods where activity was continuous for years at a time, often in the form of a churning lava lake in the crater.

• The volcano partly overlaps with two older volcanoes, Baratu and Shaheru, and is also surrounded by hundreds of small volcanic cinder cones from flank eruptions.

• Volcanism at Nyiragongo is caused by the rifting of the Earth's crust where two parts of the African Plate are breaking apart. A hot spot is probably also partly responsible for the great activity at Nyiragongo and Nyamuragira.

• The lava emitted in eruptions at Nyiragongo is often unusually fluid. Nyiragongo's lavas are made of melilite nephelinite, an alkali-rich type of volcanic rock whose unusual chemical composition may be a factor in the unusual fluidity of the lavas there. Whereas most lava flows move rather slowly and rarely pose a danger to human life,

• Nyiragongo's lava flows may race downhill at up to 60 miles per hour (up to 100 km/h). This is because of the extremely low silica content (the lava is mafic).

• Hawaiian volcanic eruptions are also characterised by lavas with low silica content, but the Hawaiian volcanoes are broad, shallow-sloped shield volcanoes in contrast to the steep-sided cone of Nyiragongo, and the silica content is high enough to slow most Hawaiian flows to walking pace.

• The lava lake activity continued through 2010. At present, the lake is mostly confined within a broad, steep-sided cinder cone on the crater floor, roughly 60 feet high by 600 feet wide.

VOLCANOES!

Well inspired by this weeks BBC program Volcano Live... i am going to start profiling the various volcanoes mentioned on the program!