Our Earth truly is art

NASA has published a number of really good e-books on planetary science. Typically, each time I stumbled on one, I added a link on my Books page, but I could not skip writing about the latest one, which I discovered thanks to this post on FlowingData. It’s called Earth as Art, and it’s a fantastic book!

The pictures in this book are truly marvellous, and a thing of art. Here are my three favourites – I am so mesmerised by them I can’t stop looking (particularly the Ugab River one).

Enjoy. Check the book, and let me know which ones you like.


Von Kármán Vortices, Southern Pacific Ocean


Ugab River, Namibia


Shoemaker Crater, Australia

Google Earth and a 5 minutes book review: Geology Illustrated

A few years ago I bought on e-bay Geology Illustrated – by John S. Shelton, for just 10 US dollars. Every time I look at, and inside the book I can’t but think those were the best 10 dollars I ever invested in books.

There are already reviews and plenty of praise for this book out there – no need to repeat any of that if not briefly. My take is that the geology is clear and well explained. A bit simple, but simple is not always bad. And Shelton himself in the preface recommends this book as a “point of departure rather than something to lean on…” but that is perfect if you are a teacher looking for material, a first year college student, or a non-geologist looking for a high quality introduction.

But the photographs are priceless, and Shelton, who was also a pilot, took them all himself. Again, the author reminds us that nothing can replace field experience, and having  been trained as a field geologist (an average one, but that’s another story) I cannot but agree. However, lacking access or time to go to the field, or both, I find looking at a book like this can be an extraordinary substitute. That is especially true if you combine the reading with using Google Earth (particularly if you are a visual-spatial learner) and that is exactly what I did.

I already praised Google Earth for visualisation in this post. This program is a fantastic tool for learning geology, and today, to reinforce the point, I want to show you a couple of examples of Google Earth views replicating almost exactly figures from Chapter 14 of Geology Illustrated: The works of streams and rivers.

The first view is a replica of Figure 130 in the book, showing a fantastic example of a stream (the Colorado River) deepening its valley at the Marble Canyon.

The second view is a replica of Figure 135, showing many excellent examples of stream capture by headward erosion. Notice that in the 60s, when the photo was taken by Shelton, the highway (US Highway 101 north of San Juan Capistrano, California) was the only visible evidence of human activity.

The last view is a replica of Figure 137 in the book, showing the meander belt of the Animas River a few miles from Durango, Colorado. Looking at this was by far my favourite as it gave me the opportunity to create my own time lapse: a repeat snapshots of the same landscape nearly 50 years apart. Tis is priceless: 50 years are nothing in geological time scale, and yet there are already some significant differences in the two images. For example, it looks like the meander cutoff  in the lower left portion of the image had ‘just’ happened in the 60s, whereas at the time the imagery used by Google Earth was acquired (I imagine in the last few years), the remnant oxbow lake is more clearly defined. Another oxbow lake in the center has nearly disappeared.

I found that this process of looking for and replicating the photos in the book, zooming in and out, then in again changing view was a fantastic way to see the geological features as part of the larger geological context, visualize them, see the interconnection with other elements of the landscape, observe how erosion and deposition, and human processes have modeled the landscape in just a few decades (as in the second and third examples).  As a geophysicist, sitting in the office away from the outcrops, this is  invaluable, and a great aid in finding analogs in support of seismic interpretations. And really you don’t need a book in your lap to start the process.

In a future post I will show my results at creating similar views using HD lidar data, which can be downloaded from the National Center for Airborne Laser Mapping, as done in this blog post on Quest.


John Shelton’s obituary, August 2008

Geomorphology from space

Image processing tips for geoscientists – 1

Today I would like to show a way to quickly create a pseudo-3D display from this map:

Original image

The map is a screen capture of a meandering river near Galena, Alaska, taken in Google Earth. I love this image; it is one of my favorite maps for several reasons. First of all it is just plainly and simply a stunningly beautiful image. Secondly, and more practically, the meanders look not too dissimilar to what they would appear on a 3D seismic time slice displayed in grayscale density which is great because it is difficult to get good 3D seismic examples to work with. Finally, this is a good test image from the filtering standpoint as it has a number of linear and curved features of different sizes, scales, and orientation.The method I will use to enhance the display is the shift and subtract operation illustrated in The Scientist and Engineer’s Guide to Digital Signal Processing along with other 3×3 edge modification methods. The idea is quite simple, and yet extremely effective – we convolve the input image with a filter like this one:

0  0  0
0  1  0
0  0 -1

Continue reading