[meteorite-list] Landslids and Lava Flows at Olympus Mons on Mars (Mars Express)

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 2 May 2013 12:32:01 -0700 (PDT)
Message-ID: <201305021932.r42JW1oC004280_at_zagami.jpl.nasa.gov>

http://www.esa.int/Our_Activities/Space_Science/Mars_Express/Landslides_and_lava_flows_at_Olympus_Mons_on_Mars

Landslids and Lava Flows at Olympus Mons on Mars
European Space Agency
2 May 2013

Giant landslides, lava flows and tectonic forces are behind this dynamic scene
captured recently by ESA's Mars Express of a region scarred by the Solar
System's largest volcano, Olympus Mons.

[Image]
Sulci Gordii in context

The image was taken on 23 January by the spacecraft's high-resolution
stereo camera, and focuses on a region known as Sulci Gordii, which lies
about 200 km east of Olympus Mons.

Sulci Gordii is an "aureole" deposit - from the Latin for "circle of light' -
and is one of many that form a broken ring around the giant volcano, as hinted
at in the context map.

The aureoles tell the story of the catastrophic collapse of the lower flanks
of Olympus Mons in its distant past. Today, it stands with steep cliff
edges that rise 2 km above the surrounding plains.

The collapse was brought about by weakening in the rocks supporting the volcanic
edifice, perhaps influenced by subsurface water. During the collapse, rocky
debris slid down and out over hundreds of kilometres of the surrounding volcanic
plains, giving rise to the rough-textured aureole seen today.

[Image]
Inside Sulci Gordii

Similar avalanches of debris are also seen surrounding some volcanoes on Earth,
including Mauna Loa in Hawaii, which, like Olympus Mons, is a smooth-sided
"shield" volcano built up from successive lava flows.

The smooth plains surrounding Sulci Gordii suggest that the massive
landslide was later partially buried by lava flows. Indeed, faint outlines
of ancient lava flows can be seen by zooming into the upper centre-left
portion of the lead high-resolution image
                                                
[Image]
Sulci Gordii close-up

The characteristic corrugated appearance of the "sulci' - a geological term
used to describe roughly parallel hills and valleys on Mars - likely resulted
during the landslide as material slid away from the volcano and became compressed
or pulled apart as it travelled across the surface. Over time, erosion of weaker
material between the peaks accentuated this effect.

The corrugated effect is best seen in the close-up perspective views. Zooming in
on these images reveals that the hills and ridges are also covered by fine wind-blown
dust, and that many small-scale landslides have occurred down the sides of the
valleys between them.

Similarly, on close inspection of the smooth plains, subtle ripples in the martian
dust blanket can be seen. Here, thin undulating dunes have been whipped
into shape by the prevailing wind.

[Image]
Channels and fractures in Sulci Gordii

Numerous sinuous channels and jagged fracture networks also crisscross the scene,
in particular at the southern (left) end of the main image and in close-up in the
perspective view above. The channels range in length from around 50 km to 300 km and
were probably widened by short-lived lava flows, or perhaps even by water.

An impressive sight on the left side of the perspective view is a sinuous channel
that is suddenly truncated by a tectonic fault. Another channel running across
the centre foreground clearly has a complex fracturing history.

[Image]
Sulci Gordii topography

In rougher terrain towards the south (top centre-right of the main image), tectonic
forces have torn apart the martian crust, most clearly visible in the colour-coded
topography map.

By studying complex regions like this - and by comparing them to similar examples
here on Earth - planetary scientists learn more about the geological
processes that dominated ancient Mars, when it was an active planet.

Just as on Earth, the scene at Sulci Gordii tells us that volcanoes can suffer
dramatic collapses that transport vast quantities of material across hundreds
of kilometres, where it is subsequently sculpted by wind, water and tectonic
forces.

[Image]
Sulci Gordii in 3D
Received on Thu 02 May 2013 03:32:01 PM PDT