Martian Volcanoes
Fires that shook me once, but now to silent ashes fall'n away.
Cold upon the dead volcano sleeps the gleam of dying day.
- Tennyson
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Animations of Martian Volcanoes |
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Mars
Introduction |
Mars is only about
one-half the size of Earth
and yet has several volcanoes that surpass the scale of the largest terrestrial volcanoes. The
most massive volcanoes are located on huge uplifts or domes in the Tharsis and
Elysium regions of Mars. The Tharsis dome is 4,000 kilometers (2,500 miles)
across and rises to 10 kilometers (6.2 miles) in height. Located on its
northwest flank are three large shield volcanoes:
Ascraeus Mons, Pavonis Mons and Arsia Mons. Beyond the dome's northwest edge is
Olympus Mons, the largest of the Tharsis volcanoes. Olympus Mons is classified
as a shield volcano. It is 24 kilometers (15 miles) high, 550 kilometers (340
miles) in diameter and is rimmed by a 6 kilometers (4 miles) high scarp. It is one of
the largest volcanoes in the Solar System. By comparison the largest volcano on
Earth is Mauna Loa
which is 9 kilometers (6 miles) high and 120 kilometers (75 miles) across.
Elysium Planitia is the second largest volcanic region on
Mars. Elysium Planitia is centered on a broad dome that is 1,700 by 2,400
kilometers (1,060 by 1,490 miles) in size. It has smaller volcanoes than the
Tharsis region, but a more diverse volcanic history. The three volcanoes
include Hecates Tholus, Elysium Mons and Albor Tholus.
The large shield volcanoes on Mars resemble Hawaiian
shield volcanoes. They both have effusive eruptions
which are relatively quiet and basaltic in nature.
Both have summit pits or calderas and long
lava flows or channels.
The biggest difference between Martian and Terrestrial volcanoes is
size. The volcanoes in the Tharsis region are 10 to 100 times larger than those
on Earth. They were built from large magma chambers deep
within the Martian crust. The Martian flows are also much longer. This is
probably due to larger eruption rates and to lower gravity. One of the reasons
volcanoes of such magnitude were able to form on Mars is because the hot
volcanic regions in the mantle remained fixed relative to the surface for
hundreds of millions of years. On Earth, the tectonic flow of the crust across
the hot volcanic regions prevent large volcanoes from forming. The Hawaiian
islands were created as the Pacific plate moved northwest. These volcanoes have
a relatively short life time. As the plate moves new volcanoes form and the old
ones become silent.
Not all Martian volcanoes are classified as shields with
effusive eruption styles. North of the Tharsis region lies Alba Patera. This
volcano is comparable to Olympus Mons in its horizontal extent but not in
height. Its base diameter is 1,500 kilometers (930 miles) but is less than 7 kilometers
(4.3 miles) high. Ceraunius Tholus is one of the smaller volcanoes. It is about
the size of the Big Island of Hawaii. It exhibits explosive eruption
characteristics and probably consists of ash deposits. Tyrrhena
Patera and Hadriaca Patera both have deeply eroded features which indicate
explosive ash eruptions. Mt. Saint Helens is
an example of a terrestrial ash eruption.
This set of images was chosen to show some of the best
examples of volcanic landforms on Mars.
Tharsis Montes
The alignment of the three shield volcanoes
that make up the Tharsis [THAR-siss] Montes region is clearly evident in this
view. They are named Ascraeus Mons (top right), Pavonis Mons (middle) and Arsia
Mons (bottom). Olympus Mons can be seen in the upper left hand corner. The
three volcanoes are each somewhat smaller than Olympus Mons, varying from 350
to 450 kilometers (220 to 280 miles) in horizontal extent and each rising about
15 kilometers (9 miles) above the surrounding plains. The Tharsis Montes are
located on the crest of a broad uplift of the Martian crust so that their
summits are at about the same elevation as the summit of Olympus Mons. The
fractures southeast of Pavonis Mons are named Noctis Labyrinthus; this region
merges with the enormous Vallis Marineris canyon system to the east. (Copyright
by Calvin J. Hamilton)
Mantle Convection
This image shows a computer simulation of processes in the interior of Mars
that could have produced the Tharsis region. The color differences are
variations in temperature. Hot regions are red and cold regions are blue and
green, with the difference between the hot and cold regions being as much as
1000°C (1800°F). Because of thermal expansion, hot rock has a lower density
than cold rock. These differences in density cause the hot material to rise
toward the surface and the cold material to sink into the interior, creating a
large-scale circulation known as mantle convection. This type of mantle flow
produces plate
tectonics on Earth.
The hot, rising material tends to push the surface of the
planet up, and the cold, sinking material tends to pull the surface down. These
motions contribute to the overall topography of the planet. This deformation of
the planet's surface is shown in gray along the outer surface of the planet in
this image. The amount of deformation is highly exaggerated to make it visible
here. The actual uplift in Tharsis is estimated to be about 8 kilometers (5
miles) at its center. This uplift also stretches the crust, forming features
such as grabens
and Valles Marineris. In addition, the hot, rising material may melt as it
approaches the surface, producing volcanic activity. (Courtesy Walter S.
Kiefer and Amanda Kubala, LPI)
Elysium Planitia
Elysium Planitia is the second largest volcanic region on Mars. It is located
on a broad dome that is 1,700 by 2,400 kilometers (1,060 by 1,490 miles) in
size. The volcanoes Hecates Tholus, Elysium Mons and Albor Tholus can be seen
going from north to south (top to bottom) in this image. Hectas Tholus is 160
by 175 kilometers (100 by 109 miles) in size with a caldera complex 11.3 by 9.1
kilometers (7 by 5.7 miles) in size. Elysium Mons is the largest volcano in
this region. It has base dimensions of 420 by 500 by 700 kilometers (260 by 310
by 435 miles) and rises 13 kilometers (8 miles) above the surrounding plains.
Its summit caldera is about 14.1 kilometers (8.8 miles) in diameter. Albor
Tholus measures 160 by 150 kilometers (100 by 93 miles) with a summit caldera
of 35 by 30 kilometers (22 by 19 miles). Its northwest flanks have been
partially buried by lava flows from Elysium Mons. (Copyright Calvin J.
Hamilton)
Olympus
Mons
Olympus [oh-LIM-pus] Mons is the largest volcano known in the solar system. It
is classified as a shield volcano,
similar to volcanoes in Hawaii.
The central edifice of Olympus Mons has a summit caldera 24
kilometers (15 miles) above the surrounding plains. Surrounding the volcano is
an outward-facing scarp
550 kilometers (342 miles) in diameter and several kilometers high. Beyond the
scarp is a moat filled with lava, most likely
derived from Olympus Mons. Farther out is an aureole of characteristically
grooved terrain, just visible at the top of the frame. (Courtesy USGS/NASA)
The Majestic Olympus
Mons
This 3D image of Olympus Mons was created using the USGS color Mars mosaic and
Mars digital elevation model. The final image shows Olympus as it would be seen
from the northeast. It is possible that volcanoes of such magnitude were able
to form on Mars because the hot volcanic regions in the mantle remained fixed
relative to the surface for hundreds of millions of years. (Copyright by
Calvin J. Hamilton)
Olympus Mons, 1998
Olympus Mons is a mountain of mystery. Taller than three Mount Everests and
about as wide as the entire Hawaiian Island chain, this giant volcano is nearly
as flat as a pancake. That is, its flanks typically only slope 2° to 5°.
The Mars Global Surveyor obtained this spectacular
wide-angle view of Olympus Mons. In this view, north is to the left and east is
up. The image was taken on a cool, crisp winter morning. The west side of the
volcano (lower portion of view, above) was clear and details on the surface
appear very sharp. The skies above the plains to the east of Olympus Mons
(upper portion of view) were cloudy. Clouds were lapping against the lower east
flanks of this 26 kilometers (16 miles) high volcano, but the summit skies were
clear. (Courtesy Malin Space Science Systems/NASA)
Olympus Mons Caldera Mosaic
This high-resolution image shows the Olympus Mons caldera located 24 kilometers
(15 miles) above the surrounding martian plains. The caldera is about 80
kilometers across with walls that are 2.4 to 2.8 kilometers deep. Calderas are
produced when the roof of the magma chamber collapses due to removal of magma
by voluminous eruptions or subterranean magma withdrawal.
This mosaic is constructed using pictures from the orbits
473S and 474S of Viking 1 near the end of its mission in 1980. As Viking 1 was
near the lowest part of its orbit and moving very fast relative to the ground
targets these pictures were shuttered using image motion compensation. (Courtesy
A. Tayfun Oner)
Ascraeus Mons Summit
This complex caldera
is composed of several discrete centers of collapse where the older collapse
features are cross-cut by more recent collapse events. The lowermost circular
floor preserves the last lava flooding event that followed the last major
collapse. The southern wall of the caldera has at least 3 kilometers (1.9
miles) of vertical relief with an average slope of at least 26° (from
horizontal). The caldera complex truncates several lava flows, indicating that
the flows predate the collapse event and that their source areas have been
destroyed by the caldera formation. (Copyright Calvin J. Hamilton; caption
by LPI)
For an 832x778 GIF image (337K) of the entire volcano
click HERE.
Arsia Mons
The caldera on Arsia Mons is considerably larger than the calderas on either
Ascraeus Mons or Pavonis Mons. However, the last major collapse event on Arsia
Mons was followed by a substantial outpouring of lava within the caldera. The
caldera rim has been breached on the southwest side while the caldera floor
lavas bury portions of the northeast rim. Aligned between these breaks in the
caldera is a series of very subdued domes on the caldera floor, perhaps
representing localized sources of the lava that flooded the caldera. The flaks
of the shield have been deeply eroded near the locations of the breaks in the
caldera rim and lava flows extend away from the volcanoes at these embayments. (Copyright
Calvin J. Hamilton; caption by LPI)
Apollinaris Patera
This view of Apollinaris Patera, shows characteristics of an explosive origin
and an effusive
origin. Incised valleys in most of the flanks of Apollinaris Patera indicates ash deposits and an
explosive origin. On the west side (left), landslides that have shaped its
surface also indicate ash deposits. Towards the south flank, a large fan of
material flowed out of the volcano. This indicates an effusive origin. Perhaps
during its early development Apollinaris Patera had an explosive origin with
effusive eruptions taking place later on. (Copyright Calvin J. Hamilton)
Ceraunius Tholus and
Uranius Tholus
Ceraunius Tholus (bottom) shows several incised valleys cut into its flanks
which indicate that it was easily eroded and probably consists of ash deposits due to explosive
activity. The lower flanks of the volcano have been buried beneath the plains
material. Ceraunius Tholus is about the size of the Big Island of Hawaii.
Uranius Tholus (Top) also shows similar characteristics to Ceraunius Tholus. A
major impact crater, just above Ceranius Tholus, postdates the plains material
and volcano. However, a prominent delta of probable volcanic material was
emplaced within the impact crater at the mouth of a sinuous channel that
extends up the flank of Cerauius Tholous to the summit crater. (Copyright
Calvin J. Hamilton; caption by LPI)
Ceraunius Tholus and
Uranius Tholus - 3D
This is a three dimensional view of Ceraunius Tholus (right) and Uranius Tholus
(left). The view is from the northwest. (Copyright Calvin J. Hamilton)
Tharsis Tholus
Tharsis Tholus measures about 150 kilometers (93 miles) across and 8 kilometers
(5 miles) high. The east and west flanks are indented giving it a strange
appearance. One possible cause for its appearance is that when the lava supply
drained away, the center of the volcano collapsed. An alternative is that big
slump areas carried off portions of the flanks, giving it the broken
appearance. (Copyright Calvin J. Hamilton)
Uranius Patera
Uranius Patera is about the size of the Big Island of Hawaii. It is about 3
kilometers (1.9 miles) in height. It has shallow slopes and lava flows. This
indicates an effusive
origin. The center caldera was formed when lava drained away and the volcano
collapsed. (Copyright Calvin J. Hamilton)
Ulysses Patera
This feature is an example of a class of volcanoes that are considerably
smaller than the broad shield volcanoes. The summit consists of a single, very
circular caldera with a smooth floor that predates the ejecta from two large
impact craters. The lower flanks of the volcano, including portions of the
impact craters, have been buried by the material that makes up the surrounding
plains. This superpositional relationship indicates that the plains were
emplaced subsequent to both the volcano and the large impact craters on the
volcano. The plains are probably made up of lava supplied from Tharsis Montes
that flowed down the sides of the broad uplift associated with the Tharsis
shields. Both the plains and the volcano are cut by a graben, indicating
tectonic activity subsequent to the emplacement of the plains. (Copyright
Calvin J. Hamilton, and LPI)
Ulysses Patera in 3D
This shows perspective view of Ulysses Patera looking from the north. (Copyright
Calvin J. Hamilton)
Tyrrhena
Patera
Volcanoes located within the densely cratered southern highlands have a very
different morphology from either the Tharsis or Elysium volcanoes. Tyrrhena
Patera has very little vertical relief (< 2 kilometers), resulting in very
shallow flank slopes. The flanks of the volcano are deeply eroded with many
broad channels that radiate from the summit region. The low relief and easily
erodible nature of the flank materials has been interpreted to indicate that
the bulk of the volcano is composed of pyroclastic ash deposits. This
interpretation implies that the style of eruption for the highland volcanoes
like Tyrrhena Patera is significantly different from the repeated effusion of
fluid lavas that built up the shield volcanoes. (Copyright Calvin J.
Hamilton; caption by LPI)
Hadriaca Patera
Much like Tyrrhena Patera, Hadriaca Patera is a deeply eroded feature having
little vertical relief. Several impact craters are superimposed on the eroded
flanks, indicating a great age for this volcano. A large channel has its source
near the southeastern margin of the volcano; the fluid that carved the channel
flowed southwest into the interior of the Hellas basin. (Copyright Calvin J.
Hamilton; caption by LPI)
Tempe Volcano
Volcanic construct on Mars are not all enormous mountains like the Tharsis
Montes. This elongate hill surmounted by a linear depression is interpreted to
be a product of localized but not extremely voluminous eruptions. If the
volcanic material was emplaced by ejection along a ballistic trajectory, this
feature may be similar to a terrestrial cinder cone. This feature is aligned
with several grabens
in the area so that a structural weakness in the crust may have provided the
conduit for the volcanic material to reach the surface. (Copyright Calvin J.
Hamilton; caption by LPI)
Hellas Mounds
Numerous small mounds having summit craters are found in various locations on
Mars. The mounds shown here are east of the Hellas basin. These features have
been interpreted to be pseudocraters created by localized phreatic explosions
where lava interacts with volatile-rich ground. Most of the mounds are between
400 meters (1,312 feet) to 1 kilometer (.62 miles) across. Many have slotlike
summit vents. However, images presently available do not have sufficient
resolution to show conclusive evidence of a volcanic origin for the mounds. (Copyright
Calvin J. Hamilton; caption by LPI)
Beatty, J. K. and A. Chaikin, eds. The New Solar System.
Massachusetts: Sky Publishing, 3rd Edition, 1990. (See Chapter 5, pp. 57-59.)
Carr M. H. "The Volcanoes of Mars." Scientific
American, 1975, 234, 32-43.
Carr M. H. The Surface of Mars. Yale University
Press, New Haven, 1981. (See Chapter 7, pp. 87-113.)
Greeley R. and Spudis P. D. "Volcanism on Mars."
Reviews of Geophysics and Space Physics, 1981, 19, 13-41.
Kiefer, Walter S., Allan H. Treiman, and Stephen M.
Clifford. The Red Planet: A Survey of Mars - Slide Set. Lunar and
Planetary Institute.
Mutch T. A., Arvidson R. E., Head J. W. III, Jones K. L.,
and Saunders R. S. The Geology of Mars. Princeton University Press,
Princeton, 1976. (See Chapter 4, pp. 151-201.)
Robinson, Mark. "Exploring Small Volcanoes on
Mars." Astronomy, April 1994, pp. 30-37.
Zimbelman, James R. Volcanoes on Mars - Slide Set.
Lunar and Planetary Institute.