Volcanic Gases

Question 1

What gas suffocated the villager near Lake Nyos?

Answer 1

Carbon dioxide

Question 2

What was the original source of gas?

Answer 2

Underground magma, gases travelled up via fissures (cracks) underneath the lake

Question 3

What triggered the release of gas from the lake?

Answer 3

A landslide, which caused CO2 rich water to rise

Question 4

Why was the gas-rich water at the bottom of the lake?

Answer 4

CO2-rich water is more dense than regular lake water

Question 5

Why was the gas white?

Answer 5

Covered in water vapor (water droplets formed on the surface of the gas)

Question 6

Was there any warning for the villagers?

Answer 6

Nope, the gas was silent and odorless

Question 7

Approx how many people died in this disaster?

Answer 7

1800 died of suffocation

Question 8

How are future disasters at Lake Nyos being prevented?

Answer 8

Several pipes vent the CO2 from the bottom of the lake to the surface

Question 9

Most of the gases in Earth’s early atmosphere came from

Answer 9

volcanoes and still contribute to the atmosphere today

Question 10

Mazuku - “evil wind”

Answer 10

• Pocket of CO2-rich air that can be lethal
• Created when CO2 accumulates in pockets low to ground

Question 11

Geology of Lake Nyos

Answer 11

• Located in the Oku volcanic field
• Disagreement about cause of volcanism: some think hot spot, others think rift-related

Question 12

What gas killed trees north of Horseshoe Lake?

Answer 12

CO2

Question 13

How much gas escapes near Horseshoe Lake each day?

Answer 13

100 tons/day

Question 14

What is the usual concentration of CO2 in the air?

Answer 14

0.035%

Question 15

What concentration of CO2 causes headaches and dizziness?

Answer 15

1%
Above 17% = death and unconsciousness in seconds

Question 16

Horseshoe Lake

Answer 16

• Summer-time exposure to high lvls of CO2 may be from lying on the ground or digging pits in the ground
• Walking through area in summer is safe as long as heads stay above ground lvl
• During the winter, CO2 lvl can build up beneath snow and CO2 gas will preferentially escape around buildings, tree wells, and depressions around large rocks

Question 17

Geology of Mammoth Mountain

Answer 17

• A lava dome made of silica-rich lavas, formed 110,000-57,000 years ago
• Lies at the edge of the Long Valley Caldera, but has a distinct magma chamber
• Volcano is still active with minor eruptions, largest was a minor phreatic (stream) eruptions 700 ya

Question 18

Earthquake swarm hits Mammoth Lakes

Answer 18

185 tremors and growing

Question 19

USGS Volcano Monitoring Program

Answer 19

Real-time monitoring of ground movements
- Thermal imaging
- Cameras
- Satellites
- Earthquake and Lahar sensors
- Surveying
- GPS
- Tiltmeter
- Airborne and ground for gas monitoring