geysers and hotsprings
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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.