21 February 2009

Using Google Earth to visualize volcanic and seismic activity

Posted by Jessica Ball

I haven’t been posting much lately (teaching labs and trying to wrap my head around volcano seismology is eating up my free time), but I have been trying to keep up with new developments. One really neat one is the release of the newest Google Earth and the Oceans layer. My last two labs have been oceanography and waves/tides/currents, so I’ve been leaning heavily on Google Earth to help my students visualize things. And it works! They’re actually engaged, especially since they get to navigate around instead of just watching me give a lecture.

The Oceans layer comes with a lot of other sublayers, including one from National Geographic about plate tectonics, earthquakes and volcanoes. Being a geology geek, I already have several volcano/earthquake layers from the Smithsonian, USGS, etc. So, I thought it might be interesting to compare the old and new offerings.

Here’s the first – the Smithsonian Global Volcanism Program’s catalog of Holocene volcanoes.

I like this layer because clicking on a volcano pops up the text of the GVP webpage on that volcano, complete with photo and links. What I don’t like about the layer is that this is all it does – nothing about plate tectonics, nothing about older volcanoes. You can see where the volcanoes are, but not (at first glance) why. Also, I’d opt for a snazzier symbol; that little X-and-box thing is efficient, but kind of boring.

Then there’s the USGS layers for earthquakes. (They don’t seem to have a volcanoes layer, but they do have an interactive map of recent activity here). One EQ layer shows earthquakes by age (i.e., in the past hour, day, week, etc.), and the other by depth. I like the clean look of these, the small legend, and the information that pops up for each earthquake, complete with links to the USGS online record and

The most recent earthquakes are shown in red (hours ago), days-old earthquakes in orange, and months-old earthquakes in yellow.

Here the shallower earthquakes are in red and orange, and the deepest are in blues and purples.

I like these because the symbols are easy to read, the legend is simple, and there’s information about tectonic plate motions (including rates of movement) and boundary locations. The layers also updates themselves each time you open up Google Earth – very useful if you’re teaching a class on plate tectonics, and want your students to keep track of earthquake activity in a particular area. You can even highlight specific types of plate boundaries, which are have their own separate sublayers.

The USGS has one more layer of historical earthquakes, with M3 in the past 90 days, M4 in the past year, and so on up to M9 (since 1970 – only one of these, the 2004 Sumatra earthquake).

No legend or drawn-out plate boundaries on this one, but a wealth of information and popups for each earthquake. It’s especially good for highlighting plate boundaries using seismic activity.

Finally there’s the new National Geographic plate tectonics layer. They went all out on this one – sublayers for plate boundaries, volcanoes, hot spots, earthquakes, plate motions…the whole shebang. It’s actually quite crowded at first. Unfortunately, to download it you have to turn on the main National Geographic sublayer of the Oceans layer, search for the NG symbol in the middle of the Pacific Ocean, and click to download the plate tectonics bit. This is a major drawback for the NG information, and in the future I hope they list their information somewhere instead of making you hunt for it on the globe.

One thing that I severely dislike about this layer is the legend. It’s far too large and covers up a significant chunk of the globe. It’s not adjustable, either, so unless you immediately memorize all the symbology, you have to keep turning it on and off. The sheer volume of information shown is also distracting – it’s better to break it down.

This one shows the plate boundary locations and types, and relative plate motions. Unlike the USGS layer, however, there’s no information about rates of movement.

This view shows some of the “Selected Hot Spots”. I’m a little iffy on whether all of the locations this layer shows are properly considered hot spots – there’s a lot of argument about these phenomena anyway. The bad thing about this layer is that beside displaying the names, there’s no pop-up info about these locations, nor is there any explanation of what a hot spot is.

This view is showing the “Notable earthquakes since 1900” and “Quakes since 1900 greater than 6.5 magnitude” layers. Again, no information about the individual events, other than marking their location. I suppose it’s useful for highlighting areas of high seismic activity, but it would be much better if there were at least magnitudes and dates listed for each event, so someone could look them up elsewhere.

And, finally, the volcanoes – small triangles are Holocene eruptions, and large ones are eruptions since 1900. Yet again, there’s no further information – this is where the Smithsonian layer outstrips the National Geographic one, despite its simplicity.

So what’s the final verdict? Use all of them! I’d reserve the National Geographic layers for general overview – showing the locations of plate boundaries, eruptions and earthquakes, for example – but use the USGS and Smithsonian layers for more in-depth examinations. The USGS layer is especially good for teaching seismology and plate tectonics, since it gives information on plate motions and individual seismic events – and links it all to the USGS database.

I’m looking forward to reviewing new layers as I find them, and hopefully I’ll get a chance to use them in my teaching.