Mapping the Earthquake in Central Mexico

The New York Times

This crowdsourced map of collapsed and damaged buildings in Mexico City (in Spanish) appeared shortly after the 7.1-magnitude earthquake hit central Mexico on 19 September [via]. NASA also produced a map, based on radar data from the ESA’s Copernicus satellites that compared the state of the region before and after the quake. Interestingly, the data was validated against the crowdsourced map.

The New York Times produced maps showing the pattern of damage in Mexico City and the extent and severity of earthquake shaking (the Times graphics department’s version of the quake’s Shake Map, I suppose) as well as how Mexico City’s geology—it was built on the drained basin of Lake Texcoco—made the impact of the quake much worse.

‘The Messed Up Mountains of Middle-earth’

Science fiction/fantasy novelist Alex Acks, a geologist by training, has some issues with Middle-earth’s mountain ranges. “Middle-earth’s got 99 problems, and mountains are basically 98 of them.” Basically it comes down to how Tolkien’s mountain ranges intersect at right angles—and mountains don’t do that.

And Mordor? Oh, I don’t even want to talk about Mordor.

Tectonic plates don’t tend to collide at neat right angles, let alone in some configuration as to create a nearly perfect box of mountains in the middle of a continent. […]

To be fair to J.R.R. Tolkien, while continental drift was a theory making headway in the world of geology from 1910 onwards, plate tectonics didn’t arrive on the scene until the mid-50s, and then it took a little while to become accepted science. (Though goodness, plate tectonics came down—I have it on good authority from geologists who were alive and in school at the time that it was like the holy light of understanding shining forth. Suddenly, so many things made sense.) Fantasy maps drawn after the 1960s don’t get even that overly generous pass.

And here I thought Tolkien’s mountains were better than most—but then I’m no geologist, and also than most may not be saying that much.

Mapping Global Landslide Susceptibility

Image: Jesse Allen. Landslide susceptibility data: Thomas Stanley and Dalia Kirschbaum (NASA/GSFC). Topographic data: SRTM. (NASA Earth Observatory)

NASA Earth Observatory notes the release of a new map of global landslide susceptibility that models the risks of landslides that are triggered by heavy rain. “The map is part of a broader effort to establish a hazards monitoring system that combines satellite observations of rainfall from the Global Precipitation Measurement (GPM) mission with an assessment of the underlying susceptibility of terrain.” [Geographical]

Mapping Fossil Sites

The PBDB Navigator is a map-based interface to the Paleobiology Database, which among other things includes the locations of every fossil find. A map of every fossil site seems straightforward enough, but there are hidden depths to this one: you can filter by taxonomy (want to look up the fossil sites for eurypterids or tyrannosaurs? no problem!) or by geologic period, but what’s especially neat is that you can factor in continental drift: when searching by geologic period (the Permian, for example), you can show the continents as they were positioned during that period (see above). More at Popular Mechanics. [Leventhal]

Marie Tharp: Continental Drift as ‘Girl Talk’

tharp-heezenAnother profile of ocean cartographer Marie Tharp, this time from’s Erin Blakemore. As Blakemore recounts, Tharp crunched and mapped the sonar sounding data collected by her collaborator, Bruce Heezen; her calculations revealed a huge valley in the middle of a ridge in the North Atlantic seafloor.

“When I showed what I found to Bruce,” she recalled, “he groaned and said ‘It cannot be. It looks too much like continental drift.’ … Bruce initially dismissed my interpretation of the profiles as ‘girl talk’.” It took almost a year for Heezen to believe her, despite a growing amount of evidence and her meticulous checking and re-checking of her work. He only changed his mind when evidence of earthquakes beneath the rift valley she had found was discovered—and when it became clear that the rift extended up and down the entire Atlantic. Today, it is considered Earth’s largest physical feature.

When Heezen—who published the work and took credit for it—announced his findings in 1956, it was no less than a seismic event in geology. But Tharp, like many other women scientists of her day, was shunted to the background.

I really ought to get to Hali Felt’s 2012 biography of Tharp, Soundings: The Story of the Remarkable Woman Who Mapped the Ocean Floor, at some point. Amazon (Kindle), iBooks.

Previously: Marie Tharp ProfileSoundings: A Biography of Marie TharpMarie Tharp and Plate TectonicsMarie Tharp.

New Orleans Is Sinking


“New Orleans and surrounding areas continue to sink at highly variable rates due to a combination of natural geologic and human-induced processes,” according to the findings of a new study that maps the rate at which New Orleans is sinking.

The maps were created using data from NASA’s Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR), which uses a technique known as interferometric synthetic aperture radar (InSAR). InSAR compares radar images of Earth’s surface over time to map surface deformation with centimeter-scale precision. It measures total surface elevation changes from all sources—human and natural, deep seated and shallow. Its data must be carefully interpreted to disentangle these phenomena, which operate at different time and space scales. UAVSAR’s spatial resolution makes it ideal for measuring subsidence in New Orleans, where human-produced subsidence can be large and is often localized.


More on Mapping Pluto’s Geology

Postdoctoral researcher Oliver White talks about creating maps of Pluto’s geology from New Horizons flyby imagery.


I have studied this area in great detail, and have defined each unit based on its texture and morphology—for example, whether it is smooth, pitted, craggy, hummocky or ridged. How well a unit can be defined depends on the resolution of the images that cover it. All of the terrain in my map has been imaged at a resolution of approximately 1,050 feet (320 meters) per pixel or better, meaning textures are resolved such that I can map units in this area with relative confidence.

By studying how the boundaries between units crosscut one another, I can also determine which units overlie others, and assemble a relative chronology (or timeline) for the different units; this work is aided by crater counts for the different terrains that have been obtained by other team members. I caution that owing to the complexity of the surface of Pluto, the work I’ve shown is in its early stages, and a lot more is still to be done.

Previously: Mapping Pluto’s Geology.

Ireland Mosaic


The European Space Agency has released this false-colour composite image of Ireland based on 16 radar scans by the Sentinel-1A satellite in May 2015. The colours show change over the 12 days of coverage: “The blues across the entire image represent strong changes in bodies of water or agricultural activities such as ploughing. […] Vegetated fields and forests appear in green. The reds and oranges represent unchanging features such as bare soil or possibly rocks that border the forests, as is clear on the left side of the image, along the tips of the island.” [ESA]

USGS Earthquake Forecast Maps Now Include Human-Induced Earthquakes


For the first time, USGS forecast maps that measure the potential damage from earthquakes in the coming year now include human-induced earthquakes, such as those caused by hydraulic fracking. (Oklahoma looms large for that very reason.) Maps for the western U.S., where a different methodology is used, presume that all earthquakes are natural in that region. [Max Galka]