1. HOT SPRINGS AND
GEYSERS
The Walker School
Physical Geology

2. 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 Grand Prismatic Spring, Yellowstone.
white geyserite, a hydrated
silicon dioxide.

3. 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.

4. 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

5. 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 pyroclastic
flows.
 Typically boils off all or most
its water before the water
reaches the surface.
 They are static and do not
change in appearance over Sampling gases at a fumarole on Mount
time. Baker in Washington, USA.
 Gasses emitted: carbon
dioxide, sulfur dioxide,
hydrochloric acid, and
hydrogen sulfide.

6. 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 Mudpot in Hverir, Námafjall, Iceland
the water table.

7. 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 Sulfurous fumaroles, Whakaari/White
creating a mud pot. Island, New Zealand
 Can dry out and revert to a
fumarole.

8. 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 Grand Prismatic Spring, Yellowstone;
because of bacteria or algae, but the largest hot springs pool in the
world.
because the water is so clear and
pure, it reflects the sunlight and
refracts it like a prism.

9. 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

10. World’s Major Known Geyser Fields
#5 Geysier,
#1 Yellowstone Haukadalur, Iceland
National Park, #2 Dolina
Wyoming Geizerov,
Kronotsky
Nature
Preserve
#3 El Tatio
El Loa Province, Chili
#4 Rotorua, Taupo
Areas, North
Island, New
Zealand

11. 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

12. 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
Iceland’s Geysir, largest fountain geyser
geyser, most are small in the world.
but a few are some of
the largest in the world.

13. 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 Yellowstone’s Crested Pool
classify them as
intermittent springs,
rather than geysers.

14. Soda Pop Geysers
 Erupt ice cold water.
 Powered by the release
of carbon dioxide.
 Interesting, but not
considered a true
geyser.
Crystal geyser, Utah

15. Thermophilic Life
 At 170 F – Thermus
aquaticus (yellow or pale
pink) Thermus aquaticus
 At 167 F – Synechococcus
and Chloroflexus (blue-
green)
Synechococcus
Chloroflexus
 At 120 F – Cyanidium
(true algae)
Cyanidium

16. 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.

17. 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.

19. Geological Requirements - Rock
 Rock below geysers are mostly
sand and gravel deposited by
rivers. Rhyolite
 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.

20. Geological Requirement - Plumbing
 Network of Underground
Fractures (maintain water
supply)
 Chambers (boiling water)
 Constrictions close to the
Surface (which help to
maintain pressure)

21. How Geysers Erupt
Eruption Indicators
•Intermittent Overflow Continues Until?
•Some Bubbling 1. Geyser runs out of water.
•Small Splashes 2. Geyer runs out of energy.
New Zealand’s Waimangu
Water needs to boil and raise the Geyers, whose name means
temperature high enough to overcome the “Black Water”, was by far the
weight of the water column. largest geyser ever known. Active
between 1900 and 1904.

22. 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
The sinter cone of Castle Geyser,
25,000 years old. Yellowstone, is dated to over 500 years.