Yellowstone Supervolcano

The Yellowstone caldera shows no signs of imminent volcanic eruption, however three giant eruptions occurred in Yellowstone in the distant past:

• 600 cubic miles of ash (2 million years ago);
• 240 cubic miles of ash (630,000 million years ago); and
• 67 cubic miles of ash (1.3 million million years ago).

Comparative Eruption Volumes
USGS Yellowstone Volcano Observatory

A volcano that ejects a volume greater than 240 cubic miles is a supervolcano.

"The lava floods and intriguing volcanoes tell us of the plasticity, mobility, of the deep interior of the globe."
— Reginald Aldworth Daly

Conditions for supervolcanoes arise when magma in a hotspot rises from the mantle into the crust but is constrained by the crust, thus allowing great pressure to build. As the magma pool grows, eventually the crust is unable to contain the pressure causing a massive explosion (e.g., Yellowstone Caldera). Supervolcanoes can also form at converging plate boundaries (e.g., Lake Toba).

"Our solid earth, apparently so stable, inert, and finished, is changing, mobile, and still evolving."
— Reginald Aldworth Daly

The USGS has studied a hypothetical Yellowstone supereruption using a model called Ash3D. Ash3D uses historical wind velocity data and estimated eruption volume to calculate the distribution and thickness of ash fall.

Ash Distribution Following a Hypothetical Month-long Yellowstone Supereruption

A distribution of ash from a hypothetical month-long Yellowstone supereruption (shown above) was modeled using January 2001 wind data.

And many a fire there burns beneath the ground.
— Empedocles

REFERENCES

• Our Mobile Earth, Reginald Aldworth Daly, 1926.
• Supervolcano, Wikipedia.
• Yellowstone supereruption would send ash across North America, Phys.org, 27 Aug 27 2014.
• Yellowstone Volcano Observatory, USGS.

Rain from Clouds

Water is continually evaporating and condensing in the sky. Clouds contain water vapor and small drops of condensed water (cloud droplets). Most of the condensed water in clouds does not fall as precipitation

Potential rain forms when water droplets condense on dust, salt, or smoke particles, which act as a cloud seeding nucleus.

When the water droplets become large enough that their fall speed exceeds the updraft speed in the cloud, they fall toward the ground. If the water drops do not evaporate as they travel earthward, they reach the ground as rain.

Virga, oil on canvas by Crystal Foreman Brown

Virga is the term for visible streaks or shafts of water that fall from clouds but evaporate before reaching the ground.

After the last of the rain had fallen from the sky and come to earth — leaving the sky clear and the earth damp and gleaming — the world below grew joyful in the cool left by the rain, and the greater clarity of life that returned with the blue of the heavens furnished each soul with its own sky.
~ Fernando Pessoa (1888-1935) from The Book of Disquiet.

Rain Drop Size

Size, fall velocity, and particle density (drops per square foot of air) vary for different types of rain (shown below).

Rain Type	Intensity inches/hour	Median diameter millimeters	Fall Velocity ft./sec.	Drops per sec. per sq. ft.
Fog	0.005	0.01	0.01	6,264,000
Mist	.002	.1	.7	2,510
Drizzle	.01	.96	13.5	14
Light rain	.04	1.24	15.7	26
Moderate rain	.15	1.60	18.7	46
Heavy rain	.60	2.05	22.0	46
Excessive rain	1.60	2.40	24.0	76
Cloudburst	4.00	2.85	25.9	113
Source: Lull, H.W., 1959, Soil Compaction on Forest and Range Lands, U.S. Dept. of Agriculture, Forestry Service, Misc. Publication No.768

Rain is grace; rain is the sky descending to the earth; without rain, there would be no life.
~ John Updike (1932-2009)

References

• USGS, The Water Cycle: Precipitation

Valley of Ten Thousand Smokes

No one alive remembers an eruption as massive as the Novarupta-Katmai Eruption of 1912. The Novarupta-Katmai eruption was the largest volcanic eruption of the Twentieth Century. This massive volcanic event occurred in Alaska in an area that was later named Valley of Ten Thousand Smokes. 

No one living today can recall a volcanic eruption of such magnitude, or of such potential disruption to human safety and systems, and yet we know that many volcanic complexes in the United States and around the globe are capable of someday erupting similar or larger volumes of molten rock and ash.
~Marcia McNutt, USGS Director

The site has been preserved since 1980 by the Katmai National Park and Preserve.

Katmai Calder - Mount Katmai, Alaska

In June of 1912, glowing hot pumice and ash spewed from the Novarupta-Katmai volcano. It flowed over terrain destroying life in its path. The ash, pumice, and gas ejected cast a haze-darkened sky over most of the Northern Hemisphere.

The Novarupta-Katmai eruption:

• Was ten times more forceful than the 1980 eruption of Mount St. Helens. 
• Buried more than 40 square miles in volcanic deposits as much as 700 feet deep. 
• Spewed 7 cubic miles of ash as far as the Mediterranean Sea. 
• Caused an acid rain that disintegrated clothes on clotheslines as far away as Vancouver, Canada.
• Reduced visibility 100 miles away in Kodiak, Alaska where for two days a person could not see a lantern held at arm's length. 

The volume of ash ejected by Novarupta-Katmai, if concentrated in one place, would be enough to bury the city of Anchorage 3 miles deep.

Volcanology is the study of volcanoes, lava, magma, and related phenomena. The term volcanology comes from the Latin word vulcanus. 

In ancient Roman religion and myth, Vulcan is the god of beneficial and hindering fire, including the fire of volcanoes. 

At the time of the Novarupta-Katmai eruption in 1912, the study of volcanic eruptions was in its infancy. Researchers had few points of comparison. Field investigations of the Katmai site provided key insights that contributed to advances in volcanology. Novarupta-Katmai has been one of the most studied eruptions in the world.

I have seen so many eruptions in the last 20 years that I don't care if I die tomorrow.
~Maurice Krafft, Volcanologist, on the day before he was killed on Unzen Volcano, Japan 1991.

Resources

Alaska Volcano Observatory - Katmai Reported Activity.
Alaska Volcano Observatory - The Great Katmai Eruption of 1912: A Century of Research Tracks Progress in Volcano Science.
USGS - The Novarupta-Katmai Eruption of 1912—Largest Eruption of the Twentieth Century: Centennial Perspectives.
Wikipedia - Valley of Ten Thousand Smokes.
Wikipedia - Vulcan (mythology).
Wikipedia - Volcanology.

Earthquake Magnitude

2012, Magnitude 8.6
Off the west coast
of northern Sumatra

Seismologists express earthquake size in units of magnitude. Magnitude is obtained from instruments called seismometers that measure motions of the ground.

The Moment Magnitude Scale is commonly used to measure the size of earthquakes.

Using the Moment Magnitude Scale, earthquake size is given in terms of the energy released based on the seismic moment of the earthquake. The seismic moment is equal to the rigidity of the Earth times the average amount of slip on the geologic fault and the size of the area that slipped.

The Moment Magnitude Scale was developed in the 1970s to replace the Richter Scale.

Shaking Amplitude

Magnitude is expressed on a base-10 logarithmic scale. An earthquake that measures 5.0 has a shaking amplitude 10 times larger than one that measures 4.0. Each whole number increase in magnitude represents a tenfold increase in measured shaking amplitude.

Energy Released

Each whole number increase in magnitude corresponds to an increase of 32 times the amount of energy released.

We learn geology the morning after the earthquake
~ Ralph Waldo Emerson

How Much Bigger?

The USGS How Much Bigger Calculator is an interactive tool that shows difference in the intensity and in energy released between two earthquake magnitudes.

Recent Large Earthquakes

The largest recorded earthquakes for each year over the past decade are shown in the table below:

Year	Date	Magnitude	Human Fatalities	Location
2012	04/11	8.6	0	Off the west coast of northern Sumatra
2011	03/11	9.0	20896	Near the East Coast of Honshu, Japan
2010	02/27	8.8	507	Offshore Maule, Chile
2009	09/29	8.1	192	Samoa Islands region
2008	05/12	7.9	87587	Eastern Sichuan, China
2007	09/12	8.5	25	Southern Sumatera, Indonesia
2006	11/15	8.3	0	Kuril Islands
2005	03/28	8.6	1313	Northern Sumatra, Indonesia
2004	12/26	9.1	227898	Off West Coast of Northern Sumatra
2003	09/25	8.3	0	Hokkaido, Japan Region

Human fatalities from seismic events depend on the magnitude and depth of the event and the proximity of the epicenter to concentrations of human population. Off-shore Earthquakes, volcanic eruptions and other underwater disturbances can cause a series of waves, or tsunamis, that can be destructive to on-shore populations.