Lecture 3 - Ring Of Fire Flashcards
Francisco Pizarro conquered what empire in 1531-1572
The inca empire
What Aztec city did Spanish conquistadors capture leading to the downfall of the Aztec civilisation. Also what year?
City of Tenochtitlán - 1521
Hernanando Cortés (1485-1547) the first conquistador told the Aztecs what?
He and his men ‘suffered from a disease of the heart which is only cured by gold’
After reaching the high Andes in 1535 what city did the conquistadors establish at the foot of Cerro Rico (mountain of the riches)?
Potosí City
The conquistadors didn’t find gold, they found silver. How did they mine this silver and how much did they make?
- in the 17thC, 160k colonists, as well as 13.5k Indians were forced to labour the mines
- In 300 years they mined, 2000 million ounces of silver, roughly £68billion
In 1964 what happened in Anchorage, Alaska
A 9.2M earthquake struck
After the 1964 quake, what USGS geologist explored Alaska
George Plafker
The town Portage was abandoned after the 1964 quake, what made the town vulnerable to flooding?
2 meters of subsidence
In the fishing village of Cordova, what was uplifted?
Harbour facilities and barnacles
What did Plafker conclude about Alaska?
That a section of the crust, 800x400km had either gone up or down
What happened to some areas of the coastline during the 1964 Alaskan earthquake?
Large tracts were uplifted, creating a new wide coastal platform or terrace
What deep trenches lie on the ocean floor of the Pacific Ocean, lie off shore and run parallel to volcanic chains or arcs?
Subduction zones
Who investigated the trenches by the Pacific Ocean?
Hugo Benioff in 1950
What was the name discovered by Hugo Benioff, that was a group of earthquake activity seismically distinct?
The Benioff zone
A subduction zone was occurring in Alaska between the relative moment of the North American and Northern Pacific Plates, what was happening?
Alaska was not riding up and over, the Pacific was sinking between the North American Plate
What created locations for deposition of rich sediments?
Former tectonic activity
What was discovered in 1968 in Northern Alaska?
The largest oil field in USA
What do recent surveys show for Yukon, Eastern Alaska?
There is potential for more oil
What can you find at subduction zones?
Active volcanoes
Name an example of an active volcano at a subduction zone?
The ice filled summit caldera of Mt. Wrangle, a large shield volcano of NE Alaska
What happened in 1975-1995 to do with world seismology?
Earthquakes marked the boundaries between tectonic plates
Plates formed the outer shell of the Earth, what is the scientific name for this?
The lithosphere
How thick is the lithosphere?
100km
When introduced in 1967 what concept was the theory of plate tectonics?
A unifying concept
What was the speed of movements of plates?
Maximum 20cm a year
More than 10cm a year
As new crust is formed at subduction zones, what happens to the old crust?
It is destroyed
When oceanic area are destroyed, what is formed?
Huge volcanoes
E.g Licancabur at the Chile-Bolivia border
What are the erupting rocks at the Chile - Bolivian border known as? And what are they named after?
Andesite
Or
Andesitic - named after the Andes Mountains
In 2002 a satellite thermal image of Chiliques volcano shows a hot spot in the summit crater, what does this mean?
It is still active
Where are volcanos found in the Andes?
Along the western margain
What is different about Andesitic volcanoes?
The compositions of lava is stick therefore super heated clouds of dust and rock are more common
Summit crater of Volcan Ollague showed what gas from a fumarole?
Helium has
Describe the process what happens at a subduction zone in the Andes
- At the oceanic lithosphere, the crust begins to melt
- Water is then released
- Molten rock is lighter so rises
- Water helps melt surrounding mantle
- Magma enriched in silica and precious metals
- Material erupts at surface
What are the two types of crust Earth has, and how thigh are they?
- Oceanic - 5-7km thick
- Continental - 30-80km thick
Continental crust is created world wide at what rate?
1km a year
