HOT SPRINGS AND

GEYSERSThe Walker School

Physical Geology

Hotsprings

A spring that is produced by the emergence of geothermally heated groundwater from the earth's crust.

Can be found in many regions of the world.

Occur where water temperature is below the boiling point.

Mineral Content: gray to white geyserite, a hydrated silicon dioxide.

Grand Prismatic Spring, Yellowstone.

Source of Heat (Non-Volcanic Origin)

Heated by geothermal heat, i.e., heat from the Earth's interior.

the temperature of rocks within the earth increases with depth. The rate of temperature increase with depth is known as the geothermal gradient.

If water percolates deeply enough into the crust, it will be heated as it comes into contact with hot rocks.

Source of Heat (Volcanic Origin)

Water may be heated

by coming into contact

with magma.

If the water only reaches

the surface in the form of

steam, it is called a

fumarole. Fumaroles escape through Fourpeaked

Glacier covering Fourpeaked Volcano

in Alaska

Details of Fumaroles

Occur along tiny cracks or long fissures, in chaotic clusters or fields, and on the surfaces of lava flows and thick deposits of pyroclasticflows.

Typically boils off all or most its water before the water reaches the surface.

They are static and do not change in appearance over time.

Gasses emitted: carbon dioxide, sulfur dioxide, hydrochloric acid, and hydrogen sulfide.

Sampling gases at a fumarole on Mount

Baker in Washington, USA.

Mudpots

If the water is mixed with mud and clay, it is called a mud pot.

Mudpots form in high-temperature geothermal areas where water is in short supply.

The thickness of the mud usually changes along with seasonal changes in the water table.

Mudpot in Hverir, Námafjall, Iceland

Details of Mudpots

Water comes from rainfall and snow melt throughout the year.

Contains fumes, like fumaroles, such as hydrogen sulfide is oxidized in the water by chemical reactions.

Contains high levels of Sulfolobus(a primitive bacteria) which forms sulfuric acid.

Sulfuric Acid attacks the rocks like strong battery acid, disintegrating the rock and creating a mud pot.

Can dry out and revert to a fumarole.

Sulfurous fumaroles, Whakaari/White

Island, New Zealand

Pools

Hot springs that have enough

water that comes to the surface to

keep the fluid from entirely

boiling away and carry away the

mud and debris.

Water is near the boiling point

and does not support the growth

of colorful bacteria or algae.

Color of some pools is not

because of bacteria or algae, but

because the water is so clear and

pure, it reflects the sunlight and

refracts it like a prism.

Grand Prismatic Spring, Yellowstone;

the largest hot springs pool in the

world.

Geysers

A geyser is a hot spring characterized by intermittent discharge of water ejected as a turbulent eruption that is accomplished by a vapor phase.

Erupts water at or usually above the boiling point.

About a thousand geysers exist worldwide, roughly half of which are in Yellowstone National Park.

Castle Geyser, Yellowstone

World’s Major Known Geyser Fields

#1 Yellowstone

National Park,

Wyoming

#2 Dolina

Geizerov,

Kronotsky

Nature

Preserve

#4 Rotorua, Taupo

Areas, North

Island, New

Zealand

#3 El Tatio

El Loa Province, Chili

#5 Geysier,

Haukadalur, Iceland

Cone Type Geysers

Most have a geyserite cone

at the ground surface.

Just below the ground is a

narrow constriction.

Often spray water during

the quite intervals between

eruptions.

Make up most of the famous

geysers around the world.

Atomizer Geyser in Yellowstone’s

Upper Geyser Basin

Fountain Type Geysers

Have open craters at the surface that fill with water during an eruption.

Steam bubbles cause bursting and spraying eruptions.

The most common type of geyser, most are small but a few are some of the largest in the world.

Iceland’s Geysir, largest fountain geyser

in the world.

Bubble Shower Springs

Undergo intermittent episodes of vigorous surface boiling because of rising superheat water.

Most are small in size, and eruptions only reach a few inches in height.

Some scientists want to classify them as intermittent springs, rather than geysers.

Yellowstone’s Crested Pool

Soda Pop Geysers

Erupt ice cold water.

Powered by the release

of carbon dioxide.

Interesting, but not

considered a true

geyser.

Crystal geyser, Utah

Thermophilic Life

At 170 F – Thermusaquaticus (yellow or pale pink)

At 167 F – Synechococcusand Chloroflexus (blue-green)

At 120 F – Cyanidium(true algae)

Synechococcus

Thermus aquaticus

Chloroflexus

Cyanidium

Geological Requirements - Water

How much water is

available (needs upwards

of 10,000 gals per

eruption)

Many require presence of

high snow melt and rain.

Yellowstone’s hot springs

require 600 million gallons

of water per day.

Old Faithful, Yellowstone National

Park requires 12 million gallons

per day.

Geological Requirements - Heat

Most geyser fields are young volcanic areas.

Water is heated by contact with the rocks and can get as hot as 650 F.

It remains liquid, rather than being vaporized, because of the high pressures and confinement of the rock strata, typically at 13,000 feet or more below the Earth’s surface.

Movement of water in the system is very slow, and water can take up to 1,100 years to travel from surface to base and back to the surface during an eruptions.

Yellowstone system releases 70 trillion calories of heat per day, which could melt 23,000 pounds of snow per second.

Geological Requirements - Rock

Rock below geysers are mostly sand and gravel deposited by rivers.

Below this layer of the geyser field, where the temperature is high and the pressure is great exist igneous rocks such as rhyolite.

Rhyolite is the source of the silica that forms greserite, which is percipitated on the wall of the hydrothermal vent.

Deposits grow at an average of 1 cm per 100 years.

Greserite, a silica, which forms

intricate patterns and beads.

Rhyolite

Geological Requirement - Plumbing

Network of Underground

Fractures (maintain water

supply)

Chambers (boiling water)

Constrictions close to the

Surface (which help to

maintain pressure)

How Geysers Erupt

Eruption Indicators

•Intermittent Overflow

•Some Bubbling

•Small Splashes

Water needs to boil and raise the

temperature high enough to overcome the

weight of the water column.

Continues Until?

1. Geyser runs out of water.

2. Geyer runs out of energy.

New Zealand’s Waimangu

Geyers, whose name means

“Black Water”, was by far the

largest geyser ever known. Active

between 1900 and 1904.

Dating Geysers

Uranium-Thorium dating

of old sinter deposits.

Radiocarbon dating of

petrified wood.

Belong to recent

volcanic activity; most

range from 10,000 to

25,000 years old. The sinter cone of Castle Geyser,

Yellowstone, is dated to over 500 years.