Curiosity heads off to Mars

On Saturday 26th November the Mars Science Laboratory mission launched safely from Florida. It should land on Mars in early August next year, ready for the amazingly well-equipped Curiosity rover vehicle to start its exploration of Gale Crater.  The aim of the mission is to search for signs that conditions  might once have been favourable for life, by looking for evidence in the sedimentary rocks found in the crater.  Geomorphology will play an important part of this mission, and geomorphologists will also learn a lot from it.  Already there are many links between planetary science and terrestrial geomorphology. For example, much of our understanding of the surface conditions on Mars comes from looking at what the Americans call 'analog' environments - i.e. places on Earth that are similar to places on Mars, such as Antarctica and hyper-arid deserts such as the Atacama and the Namib deserts.

HiRise image of barchan dunes on Mars

Also, as the above image shows we can now see an amazing range of landforms on Mars which are leading geomorphologists to ask all sorts of questions about how they are formed.

The IAG Planetary Geomorphology Working Group posts monthly images with accompanying  explanations most of which deal with some aspects of comparisons between landforms and processes on Earth and Mars.  Check out the collection at the following address - especially the one from December 2010 on rock breakdown on Earth and Mars which I put together.

http://www.psi.edu/pgwg/images/index.html

Geomorphologists on Earth are highly envious of the equipment that the Mars Science Lab mission has on-board the Curiosity Rover.  Have a look at the NASA factsheet (link below) to find out all the information about the physical and chemical make-up of the rocks that Curiosity will be able to glean in the field.

http://www.jpl.nasa.gov/news/fact_sheets/mars-science-laboratory.pdf

Fingers crossed, if all goes to plan, Curiosity and the Mars Science Lab mission should start sending back some new and intriguing data next summer, which will not only throw further light on its geological, geomorphological and possibly biological history.

San Pedro landslide - a slow build up to a dramatic event

San Pedro is on the Palos Verdes peninsula just south of Los Angeles - and in Sunday 20th November 2011 a slow-moving landslide which had been moving at a few 10s of mms per day for several months suddenly failed dramatically in a few minutes. A 200m stretch of the main Paseo del Mar road slid away from the clifftops, dropping some 30m.  It's a beautiful hilly area, with upmarket housing and fantastic coastal views.  It's also a hotspot for landslides, as evidenced by the excellent California Geological Survey landslide map produced in 2007 which you can access at:
ftp://ftp.consrv.ca.gov/pub/dmg/pubs/lsim/LSIM_PalosVerdes.pdf
Be patient as it is a large file and takes some time to download.  if you read the text on the right hand side of the map you'll find out more about why the area is prone to landslides.  The essential reasons are:

1. The peninsula is underpinned by Miocene rocks, including shale.  Many of the landslides are located on the easily erodible shale.
2. The peninsula is crossed by the Palos Verdes fault and folded into a complex anticlinal structure.

Human activities have also been blamed for the high occurrence of landslides here. Not only building extensively on the clifftops, but also mis-managing drainage systems and, one factor quoted in the local news as being responsible for the most recent event - cold war underground missile silos are allegedly found in the area.  On Sunday 20th November 2011 it was a horrendously rainy day in Los Angeles - over 20mm of rain fell in a few hours.  

You can explore the coast on Google Maps below - the site of the 20th November 2011 landslide is at the centre of the view - but if you head N and W up the coast you can see vast numbers of houses and impermeable concrete structures along the clifftops.  Surely asking for trouble?


View Larger Map

Think about how would describe the causes of this landslide, using Mike Crozier's predisposing, triggering and maintaining factors framework. Was the rainstorm on November 20th the trigger? Or not?

Landscapes as palimpsests

Geomorphologists often use the term 'palimpsest' to describe the landscape or terrain we see around us.  What they mean by this is that the landscape has been shaped by many periods of geomorphic change, each change acting upon a surface that has been already altered by previous processes.  In many cases, evidence of the former processes can be seen partially hidden by the most recently produced landforms.  For example, Quaternary glaciations deposited till and other material over much of the lowlands of Britain - which partially obscured landforms produced in the Tertiary period.  In some cases pre-existing topography such as folded landscapes produced by tectonics influences the location of later erosion and sedimentation.

An example of folding of Miocene sediments, producing a syncline over which later Quaternary sediments have been deposited.  From the Mojave Desert, California.  

But where does this term 'palimpsest' come from and what does it mean?  A palimpsest comes for the Greek for 'scraped again' and is used by historians to refer to manuscripts (often written on parchment or vellum) which have been rubbed out and new texts written over the top.  Often this process has been repeated many times.  A good example, which forms the basis of an exhibition at the Walters Art Museum can be found described and illustrated at:

http://archimedespalimpsest.org/about/

Geomorphological time scales

As I mentioned in one of my first lectures, it is important to get to grips with the geological time scale.  The version reproduced below is a useful one for geomorphologists.

Most (but not all) of the land surface we see around us has been predominantly sculpted by geomorphic processes over the last 65 million years - the period filled by the column on the right hand side of the timescale as shown above.  Indeed, in many places the Quaternary period (the last 2.4 million years or so or the top sliver of the right hand column) has seen the major landscape evolution.

Tibetan plateau uplift and its impacts on China

The impressive uplift of the Tibetan plateau over the Quaternary period (averaging just over 1mm a year - sounds slow, but for long term uplift this is spectacular!) has had important consequences for the landscape, climate and ecology of China.  These impacts are nicely and simply explained in this article by Dianfa Zhang and colleagues in 2000 in Environmental Geology:

http://activetectonics.asu.edu/teaching/GLG494-ICOG/Tibetan%20Plateau.pdf

Check it out as it will help you understand the complex links between tectonic uplift, denudation and climate.

Canary Islands volcanic activity

Recent subsea volcanic activity has been reported off El Hierro the smallest and newest island in the Canaries off NorthAfrica (see my lecture on tectonics and geomorphology for more details about the Canaries).  The latest reports record 'jacuzzi' like disturbances of the sea off El Hierro as hot basaltic lava is being produced, and worries of a potential tsunami also float around the blogosphere.  The events remind us of the importance of volcanic activity in shaping oceanic island geomorphology.  Check out the latest reports at:
http://www.wired.com/wiredscience/2011/11/renewed-eruptions-at-el-hierro-in-the-canary-islands/#more-85516

Dauphin Island, Alabama...storms, plants and animals shaping the coast

A good example of climatic and ecological influences on geomorphic processes comes from the coastal barrier islands of the Gulf Coast of USA, where I recently attended a conference.  Dauphin Island, Alabama, for example, was badly affected by Hurricane Katrina, which cut off the west side of the island completely. The image from Google Earth below shows what the island looks like today. If you scroll to the west you will, eventually, find the western tip of the island which is now separated from the rest by some distance.


View Larger Map

The USGS have carried out extensive surveys of Dauphin Island before and after Hurricane events - check out this website for some really good images and explanations of the impact of Hurricane Katrina:
http://coastal.er.usgs.gov/hurricanes/katrina/lidar/dauphin-island.html

As a result of day to day coastal processes the island is constantly changing, and hurricanes regularly 'reset' the sediment stores.  However, organisms also play a big role here - both erosive and protective. The local authorities are currently using plants to aid sedimentation on the backshore dunes - as shown in the image below. They discourage walking over the dunes, as this damages the vegetation and releases sand.

'These dunes aren't made for walking' 

Further down the beach, there is widespread evidence of organisms (probably crabs) causing widespread mobilisation of sediment through extensive burrowing activity.

The results of an energetic burrowing crab

The question for geomorphologists is how to quantify in a meaningful way the different contributions of plants and animals to moving and storing sediment here, and to compare them waves and winds (all low magnitude and high frequency processes) and also with the high magnitude-low frequency impacts of storms and hurricanes. How would you do that?

Thanks to Dr Carole Sawyer, University of South Alabama for introducing me to Dauphin Island.

Online geomorphological vignettes

No, I didn't know what a 'vignette' was either, until I came across this website
http://serc.carleton.edu/vignettes/index.html
which has a whole series of short articles on key topics in geomorphology.  They have a strong USA flavour (or should that be 'flavor') to them, but many are helpful case studies of tectonic, climatic and other influences on geomorphology.  Explore them and see what you think.

I found this one particularly interesting as it deals with the indirect control of climate change on erosion through the climatic influence on vegetation:

Links between climate change, vegetation and erosion in Australia during the last 100,000 years

Anthony Dosseto
University of Wollongong

Kate Maher (Stanford University), Paul Hesse, Kirstie Fryirs and Simon Turner (Macquarie University)

Darwin's earthworm experiments

As I mentioned in my 'Ecology and geomorphology' lecture Charles Darwin really started the ball rolling on investigating the impacts plants and animals make on geomorphic processes.  He did this largely through his experimental studies on earthworms and the amount of sediment they move.  His work is highly important in providing one of the very first (and still a well-cited) set of figures quantifying how much geomorphic work earthworms do.  One of the key tasks awaiting geomorphologists today is to provide further datasets on different species, such as badgers, turtles, ants, gophers, ground squirrels, moles, packrats...I could go on...

Here's an interesting article and radio story about Darwin's earthworm experiments and follow-up work that has been done on them:
http://www.npr.org/templates/story/story.php?storyId=100627614

Paraglacial processes shaped the Lake District

..well, partly at least!  This paper by Peter Wilson nicely documents five rock slope failures in the Lake District and, based on quite detailed fieldwork (don't get bogged down in the details), suggests that they are of paraglacial origin.  My lecture on 'Climate, climate change and geomorphology' introduced the concept of paraglaciation, and this paper should help to bring it to life.  When you look at the paper, think about the sources of evidence Wilson uses and what other evidence would be really useful to test whether or not the rock slope failures actually WERE a result of paraglaciation.  You can access a pdf of the paper at:

http://www.science.ulster.ac.uk/ae/docs/Peters%20papers/Wasdale.pdf

Landslides in action

There are lots of good resources about landslides and other mass movements available on the web.  The best is the Landslides Blog by Prof Dave Petley, University of Durham.http://blogs.agu.org/landslideblog/

He updates it regularly and it contains some excellent examples and explanations of mass movements and their impacts from around the world.

There's also a good You Tube video of a recent dramatic cliff collapse in Cornwall which is well worth looking at http://youtu.be/ZVjr4mii3cE

Ecology and geomorphology - the search for a signature of life on Earth

As my lecture on  'Ecology and Geomorphology' demonstrated, there are many direct and indirect ways in which vegetation, animals and microorganisms influence geomorphology.  Beavers create dams which affect whole water courses, badgers burrow and cause huge amounts of sediment to be moved around hillslopes, whilst vegetation can protect many soil surfaces from wind and water-based erosion.  But does all this biogeomorphic effort actually add up to anything recognisable?  Is there a signature of life on Earth? These questions have received much attention from geomorphologists over recent years, as evidenced by this paper by Dietrich and Perron which is well worth looking at.  Read it and see what you think...

The search for a topographic signature of life.

Dietrich WE, Perron JT.  Nature 2006, 439: 411-418

Abstract

Landscapes are shaped by the uplift, deformation and breakdown of bedrock and the erosion, transport and deposition of sediment. Life is important in all of these processes. Over short timescales, the impact of life is quite apparent: rock weathering, soil formation and erosion, slope stability and river dynamics are directly influenced by biotic processes that mediate chemical reactions, dilate soil, disrupt the ground surface and add strength with a weave of roots. Over geologic time, biotic effects are less obvious but equally important: biota affect climate, and climatic conditions dictate the mechanisms and rates of erosion that control topographic evolution. Apart from the obvious influence of humans, does the resulting landscape bear an unmistakable stamp of life? The influence of life on topography is a topic that has remained largely unexplored. Erosion laws that explicitly include biotic effects are needed to explore how intrinsically small-scale biotic processes can influence the form of entire landscapes, and to determine whether these processes create a distinctive topography.

Why does geomorphology matter?

Geomorphology shapes the world around us, and in turn we have a dramatic impact on much of the landscape through our influence on earth surface processes.  This is, in a nutshell, one of the major reasons geomorphology matters.  An interesting recent example of the key influence of geomorphology, in this case tectonic geomorphology, on humans comes from an article in the Journal of Human Evolution by Bailey et al.  In it, they illustrate how tectonic processes made a clear difference to the early hominids in South Africa.  A simple news item on the findings of the paper can be found at:
http://www.sciencedaily.com/releases/2011/03/110303065358.htm

Further details can be found by reading the paper as a whole,

Landscapes of human evolution: models and methods of tectonic geomorphology and the reconstruction of hominin landscapes

Geoffrey N. Bailey, Sally C. Reynolds,  Geoffrey C.P. King

Journal of Human Evolution 2011, 60: 257-280

Abstract

This paper examines the relationship between complex and tectonically active landscapes and patterns of human evolution. We show how active tectonics can produce dynamic landscapes with geomorphological and topographic features that may be critical to long-term patterns of hominin land use, but which are not typically addressed in landscape reconstructions based on existing geological and paleoenvironmental principles. We describe methods of representing topography at a range of scales using measures of roughness based on digital elevation data, and combine the resulting maps with satellite imagery and ground observations to reconstruct features of the wider landscape as they existed at the time of hominin occupation and activity. We apply these methods to sites in South Africa, where relatively stable topography facilitates reconstruction. We demonstrate the presence of previously unrecognized tectonic effects and their implications for the interpretation of hominin habitats and land use. In parts of the East African Rift, reconstruction is more difficult because of dramatic changes since the time of hominin occupation, while fossils are often found in places where activity has now almost ceased. However, we show that original, dynamic landscape features can be assessed by analogy with parts of the Rift that are currently active and indicate how this approach can complement other sources of information to add new insights and pose new questions for future investigation of hominin land use and habitats.

Tectonics and climate: the great geomorphic battle

The twin controls of climate and tectonics are the major forces shaping the geomorphological landscape around us.  Much recent geomorphic work has gone into clarifying which is the most important, and how they interact.  Many recent studies focus in particular on the relationship between tectonic uplift and climatically-powered denudation in shaping mountains.  There are several good papers you can look at to find more about this topic, but I recommend as a starting point this paper by Egholm et al:

Glacial effects limiting mountain height.

Egholm DL, Nielsen SB, Pedersen VK, Lesemann JE.

Abstract

The height of mountain ranges reflects the balance between tectonic rock uplift, crustal strength and surface denudation. Tectonic deformation and surface denudation are interdependent, however, and feedback mechanisms-in particular, the potential link to climate-are subjects of intense debate. Spatial variations in fluvial denudation rate caused by precipitation gradients are known to provide first-order controls on mountain range width, crustal deformation rates and rock uplift. Moreover, limits to crustal strength are thought to constrain the maximum elevation of large continental plateaus, such as those in Tibet and the central Andes. There are indications that the general height of mountain ranges is also directly influenced by the extent of glaciation through an efficient denudation mechanism known as the glacial buzzsaw. Here we use a global analysis of topography and show that variations in maximum mountain height correlate closely with climate-controlled gradients in snowline altitude for many high mountain ranges across orogenic ages and tectonic styles. With the aid of a numerical model, we further demonstrate how a combination of erosional destruction of topography above the snowline by glacier-sliding and commensurate isostatic landscape uplift caused by erosional unloading can explain observations of maximum mountain height by driving elevations towards an altitude window just below the snowline. The model thereby self-consistently produces the hypsometric signature of the glacial buzzsaw, and suggests that differences in the height of mountain ranges mainly reflect variations in local climate rather than tectonic forces.

Nature. 2009 460:884-7.

The San Andreas fault



Looking west from Joshua Tree, with the San Andreas fault running straight across in the middel distance

 One of the many advantages of being on sabbatical in Los Angeles is the opportunity to visit some prime geomorphological sites.  On a recent trip to the Joshua Tree National Park I had this great view over the San Andreas Fault from a local viewpoint.  As you can see the fault really does have a clear landscape presence.

Himalayan tectonics and landscape

There are lots of reports and papers about the Himalayas and the Tibetan Plateau, which I will refer to in susbequent posts, but perhaps a good starting point is the on-line chapter from the book 'Geomorphology from Space' which you can find at: http://disc.gsfc.nasa.gov/geomorphology/GEO_2/GEO_PLATE_T-48.shtml  This shows lots of good imagery and gives you a basic explanation of the relief here.

Welcome to this blog

This blog accompanies the 5 lectures for Prelims geomorphology given by podcast by Heather Viles.  These lectures cover:

1. Introduction to geomorphology
2. Tectonics and geomorphology
3. Climate, climate change and geomorphology
4. Ecology and geomorphology
5. Mass movements and slopes

The posts on the blog will provide some more information and links to these and other key geomorphological topics.  I hope they are useful...