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GEOPHYSICAL RESEARCH LETTERS, VOL. 33, L13201, doi:10.1029/2006GL026396, 2006
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Geologically recent tectonic, volcanic and fluvial activity on the eastern
flank of the Olympus Mons volcano, Mars
A. T. Basilevsky,1,2 S. C. Werner,2 G. Neukum,2 J. W. Head,3 S. van Gasselt,2
K. Gwinner,4 and B. A. Ivanov5
Received 23 March 2006; revised 31 May 2006; accepted 6 June 2006; published 11 July 2006.
[1] We show evidence of very recent (25– 40 Myr)
geologic activity on the eastern flank of Olympus Mons
volcano that includes a suite of fluvial (channel networks),
volcanic (emplacement of lava flows and dikes), and
tectonic (wrinkle ridges and troughs) processes. The
combination and youth of these features confirms the
importance of geological activity continuing to the present
on Mars. Citation: Basilevsky, A. T., S. C. Werner, G. Neukum,
J. W. Head, S. van Gasselt, K. Gwinner, and B. A. Ivanov (2006),
Geologically recent tectonic, volcanic and fluvial activity on the
eastern flank of the Olympus Mons volcano, Mars, Geophys. Res.
Lett., 33, L13201, doi:10.1029/2006GL026396.
1. Introduction
[2] Photogeologic analysis of High Resolution Stereo
Camera (HRSC) images of the eastern flank of Olympus
Mons volcano and adjacent lowland plains (orbit 1089;
Figure 1), aided by HRSC-derived high-resolution digital
terrain models [Gwinner et al., 2005], as well as MOC and
MOLA data have provided new insight into the geological
processes operating on the surface and flanks of Olympus
Mons. This study continues our analysis of the western
flank of the volcano [Neukum et al., 2004; Basilevsky et al.,
2005]. In this study we used mostly the nadir channel
images (12.5 m/px, Sun elevation 52° to 55°). An essential
part of this study was the estimation of the surface ages
through impact crater counts of subareas, using both HRSC
and MOC images and the updated model of cratering
chronology [Hartmann and Neukum, 2001].
2. Observations
[3] On the eastern flank, the surface above the steep
volcano slopes (the summit plateau) shows lava flows
almost everywhere, each typically with an apparent length
of a few km and widths of a few hundred meters, and their
surfaces inclined 2 to 5°. Impact crater counts show that
the flows are 190 – 200 Myr old with a signature of a
500 Myr old episode (Figure 1). At this position on the
1
Vernadsky Institute of Geochemistry and Analytical Chemistry,
Moscow, Russia.
2
Department of Earth Sciences, Freie Universität Berlin, Berlin,
Germany.
3
Department of Geological Sciences, Brown University, Providence,
Rhode Island, USA.
4
Institut für Planetenforschung, Deutsches Zentrum fur Luft- und
Raumfahrt, Berlin, Germany.
5
Institute of Dynamics of Geospheres, Moscow, Russia.
Copyright 2006 by the American Geophysical Union.
0094-8276/06/2006GL026396$05.00
summit plateau in the western flank of Olympus, several
small mesas were observed. In contrast, on the east, only
one large mesa-like feature is seen. Its surface stands 200 to
650 m above the neighboring plateau areas and is covered
by lava flows, whose patterns are practically identical to
those in the areas outside the mesa. Contrary to what was
observed in the west, almost no layers are seen here in the
mesa slopes and no evidence of mesa surface collapse is
observed [Basilevsky et al., 2005]. In some places on the
mesa slopes, down-slope-trending dark streaks are seen
suggesting the presence of a dust mantle [Sullivan et al.,
2001]. The dust mantle suggested by the dark streaks is
consistent with the generally low thermal inertia of this area
[Mellon et al., 2000].
[4] Slopes on the western part of the Olympus Mons
scarp were classified into three morphological types
[Basilevsky et al., 2005]: (1) the steepest slopes with flutes
and ravines; (2) less steep slopes with chaos-like depressions from which channel-like grooves trend downhill; and
(3) the gentlest slopes, covered by lava flows continuing
from the summit plateau to the lowland plains. Beneath type
1 and 2 slopes vast flow-like features, interpreted as
possible glaciers, have been mapped. They were considered
by Lucchitta [1981] and then by Milkovich et al. [2006] to
be formed by glaciers. On the eastern flank of Olympus
Mons, slopes of type 2 are absent. Slopes of types 1 and
type 3 are abundant in the east, and in addition, a new
(fourth) slope type appears when lavas flow over the rims of
type 1 slopes. Beneath the slopes of the eastern flank, no
vast glacier-type features have been observed.
[5] Within the study area the lowland plains typically
have a smooth surface only locally complicated by readily
or poorly-visible lava flows. Locally, patches of slightly
brighter and darker surfaces have streak-like outlines and
appear to be of eolian origin. The plains surface is inclined
0.5° southwestward on average, but locally slopes up to a
few degrees are present.
[6] In the southern part of the plains, a few networks of
channels typically starting from steep-walled forking and
branching troughs are seen (blue lines in Figure 1). The
channels intersect, anastomose and form networks. Channels are typically 250 – 350 m wide, although in some places
they widen up to 1.7– 2.5 km. Their depth, measured from
individual MOLA profiles, varies from 8 to 40 m [Pupysheva
et al., 2006]. The largest network (10 km 60 km) starts
from a 1 km wide and 200 m deep arcuate trough. Some
channels are single and resemble tectonic troughs and lunar
rilles. They often have levees and are fringed with lava
flows (Figure 2a). The morphology of a significant part of
the channels, including the presence of streamlined islands
and terraces (Figures 2b– 2d), resembles that of martian
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Figure 1. (top) Geomorphic map of the eastern flank of Olympus Mons volcano and (bottom) crater count plots. Dark red
outlines – lava flows; bright red – wrinkle ridges; blue – channels; green – domes and ridges above features interpreted to
be dikes; white – landslide(?) accumulations; light blue fields – mesa and adjacent hills; red numbers are crater ages.
outflow channels [Baker, 1982; Carr, 1996]. Within the
channels no evidence of significant eolian or other resurfacing is seen.
[7] Our crater counts (Figure 1) show that the surface age
of the network-bearing plains varies from 30 to 145 Myr.
Based on three independent crater counts made by us, the
channel floors have been dated as 25– 40 Myr old. The
differences between the channel age estimates and those for
the lava covered plateau (the first are significantly younger)
are statistically reliable at the level better than 3 sigma. The
range of ages for the plains obviously reflects different
episodes of lava emplacement and eolian resurfacing.
[8] Wrinkle ridges are observed (red lines in Figure 1) on
the lowland plains, locally on the volcano slope and at the
edge of the summit plateau. They are 100– 300 m wide and
up to 50 – 100 m high. Wrinkle ridges are commonly
interpreted to be the result of compressional deformation
[e.g., Mueller and Golombek, 2004]. In some places at the
foot of the volcano slope, wrinkle ridges border arch-like
terraces 100 – 200 m high. In one such place we see a
channel crossing the 150– 200 m high terrace (Figure 3).
Here the orientation of the streamlined islands suggests that
the channel-forming flow direction was toward a direction
that is now uphill. We interpret this as evidence that the
Figure 2. Parts of the channel network in the lowland plains east of Olympus scarp. Arrows show the erosional terraces.
(a and b) Portions of HRSC image (nadir). (c and d) MOC images M22-01909 and R16-01228. Figure 2c is the outlined
area shown in Figure 2b, and Figure 2d is the outlined area shown in Figure 2c.
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et al. [2005] in the crater Huygens and Pavonis Mons areas
(Figures 4e and 4f) and interpreted as the exhumed tops of
magmatic dikes.
3. Discussion
Figure 3. Section of the channel network uplifted by
wrinkle ridging. MOC image M03-03753. Small white
arrow – streamlined islands; large white arrows – the
deduced flow direction; black arrows – wrinkle ridges.
wrinkle-ridged terrace formed after the channel incision as
the result of tectonic deformation. Thus we interpret the
wrinkle ridging here to have occured more recently than
25– 40 Myr ago.
[9] In the HRSC and MOC images of the lowland plains
chains of dome-like hills are observed locally (Figures 4a
and 4b). These are typically a few tens to 100 – 150 m
across, up to a few tens of meters high and resemble in their
morphology spatter and cinder cones formed along fissure
eruptions of basaltic lava on Earth. Locally, these features
are superposed on channels, so their emplacement occured
more recently than 25 –40 Myr ago. Similar chains of hills
have been described by Head et al. [2005] in the Arsia
Mons area (Figure 4c) and interpreted as spatter cones at the
tops of magmatic dikes. Locally the dome-like hills are
interconnected by linear ridges (black-and-white arrow in
Figure 4b) and several ridges that are significantly more
rectilinear than normal wrinkle ridges are observed without
connection to the chains of hills (Figure 4d). Similar linear
ridges have been described by Head et al. [2006] and Shean
[10] Our observations of the western and eastern flanks of
Olympus Mons support the traditional interpretation of this
mountain as a very large basaltic shield volcano [e.g., Carr,
1973; Greeley and Spudis, 1981; Morris and Tanaka, 1994].
On the western flank we have also found evidence of
involvement of dust-and-ice airborne deposits in the accumulation of the Olympus Mons construct. These deposits
are partly seen as mesas composed of prominently layered
material, which when in contact with lava flows, shows
evidence of collapse [Basilevsky et al., 2005].
[11] The mesa on the eastern-flank and the adjacent hills
do not show such layering. This, however, could be due to
masking by the dust mantle. The observation that the easternflank mesa material does not show evidence of collapse when
in contact with lava flows, suggests that ice, if present, is not a
significant component here. The absence of vast glacier-type
features in the east-flank plains also suggests a smaller
(if any) involvement of ice deposition in the geological
processes here.
[12] A significant part of channels of the east-flank plains
show morphologic similarity to large-scale outflow channels.
The latter are traditionally considered to be the result of largescale water erosion [Baker, 1982; Carr, 1996]. Recently, this
interpretation has been challenged by the suggestion that
highly fluid lavas could have cut the channels [Leverington,
2004]. In the study area we do see evidence that some
‘‘simple’’ channels were filled with lava and perhaps cut by
lava, whose flows we see as flanking the channel (Figure 2a).
[13] The majority of the channels of the study area,
however, show well developed streamlined islands and
terraced slopes (Figures 2b– 2d), suggesting a leading role
of water erosion. Such features are much less prominent in
lava channels of the Moon and Venus (see summary by Baker
Figure 4. Chains of volcanic domes (a and b) east of Olympus Mons (white arrows) and (c) on Arsia Mons and linear
(white arrows) and wrinkle (black) ridges (d) east of Olympus Mons and (e and f) NE of crater Huygens, all as surface
expressions of dikes. Figures 4a and 4d are HRSC images; Figures 4b and 4c are MOC images M22-01909 and S07-01314;
Figure 4e is THEMIS image I08224016; and Figure 4f is MOC image E02-01479. Figure 4b is the outlined area in Figure
4a, and Figure 4f is the outlined area in Figure 4e.
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et al. [1992]). Mouginis-Mark [1990], who first described the
channels east of Olympus Mons, favored the hypothesis that
they were water cut. Similar considerations has been recently
published for the Atabasca Vallis channels, resembling the
channels studied by us [e.g., Burr et al., 2002; Plescia, 2003;
Head et al., 2003]. So we believe that the majority of
channels have been cut by water released due to dike
emplacement, cracking of the cryosphjere, and flow of deep
groundwater through the crack [Head et al., 2003].
[14] Wrinkle ridges on Mars are typical for Hesperian
plains [e.g., Mueller and Golombek, 2004] while in the
study area they were forming toward the end of the
Amazonian period. This compressional deformation could
be due to the load of the Olympus Mons construct [e.g.,
McGovern and Solomon, 1993].
[15] Recent dike emplacement in the east-flank plains
could be related to the activity of the Olympus volcano,
whose latest episodes were interpreted to have been very
recent [Neukum et al., 2004]. But because only part of the
features interpreted to be dikes are radial to the volcano, the
dike-forming magmas could also come from another closely-located source, as appears to be the case for the recent
Arsia eruptions [Head et al., 2005].
[16] An important conclusion of this work is finding a
very young age for several geologic processes. The key
evidence for this are crater counts on the channel floor.
Although the crater-count areas are relatively small, the
numbers of craters counted in three independent counts on
the HRSC and two MOC images were not small: 115, 130
and 180. The data points fit well the isochrons (see the plots
in Figure 1). If these areas are contaminated by secondary
craters, an issue now actively discussed [e.g., McEwen et al.,
2005], the surface would be even younger. So we believe
that in these given areas the effects of possible secondary
craters are minor and thus, these geologic processes operated
at the very latest part of the Amazonian period.
4. Conclusion
[17] Our observations and analysis on the eastern flank of
the Olympus Mons provide evidence of a very recent suite
of fluvial (channel networks), tectonic (wrinkle ridges and
troughs), and volcanic (lava flows and dikes) processes.
Their youth is interesting from the point of view of
continuity of geologic activity in the history of Mars. The
extremely long duration of the Olympus Mons volcanic
activity (since 3.9 Gyr until the very recent [Hartmann and
Neukum, 2001; Neukum et al., 2004]) implies correspondinly long potential hydrothermal activity, and this may
provide the basis for this area to be a candidate longduration martian life habitat.
[18] Acknowledgments. We acknowledge DFG and NASA financial
support, the help of the ESTEC and ESOC staff, the DLR Experiment and
Operation Team and the HRSC CoI Team as well as help of U. Wolf
with crater counts and dating, discussions with C. Fasset, E. Hauber,
M. Kreslavsky, R. Kuzmin, and reviews of Victor Baker and Nadine Barlow.
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A. T. Basilevsky, Vernadsky Institute of Geochemistry and Analytical
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K. Gwinner, Institut für Planetenforschung, Deutsches Zentrum fur
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J. W. Head, Brown University, Department of Geological Sciences,
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G. Neukum, S. van Gasselt, and S. Werner, Freie Universität Berlin,
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