<p>The revolution in how we survey and image the surface of the Earth has had profound impacts on the geosciences. This shouldn’t be a shock to anyone as that’s what geoscientists do — study the Earth — and as we get more and better data on the planet and its surface, the better our understanding will become (and the more questions we can ask). Few technological leaps have been more important to geosciences than satellite imaging of the Earth.</p><p>That is more than just taking cool pictures of the planet, but also collecting location and elevation data of the surface … and being able to do so in sub-centimeter precision and repeatedly over intervals of days (or less). Combine that with land-based tools like LIDAR (Light Detection and Ranging), and suddenly we can notice very small changes in the Earth’s surface. Dump all this data in a geographic information system ...</p>

September 2006 MODIS image of southern California taken by the Aqua satellite. NASA Earth Observatory.

Explore satellite imaging of the Earth and how new techniques reveal subtle changes in our planet's surface, including the Palmdale Bulge.

Planet Earth

The Palmdale Bulge: A Geo-Crisis That Likely Never Existed

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News

Erik Klemetti

Science

The revolution in how we survey and image the surface of the Earth has had profound impacts on the geosciences. This shouldn’t be a shock to anyone as that’s what geoscientists do — study the Earth — and as we get more and better data on the planet and its surface, the better our understanding will become (and the more questions we can ask). Few technological leaps have been more important to geosciences than satellite imaging of the Earth. That is more than just taking cool pictures of the planet, but also collecting location and elevation data of the surface … and being able to do so in sub-centimeter precision and repeatedly over intervals of days (or less). Combine that with land-based tools like LIDAR (Light Detection and Ranging), and suddenly we can notice very small changes in the Earth’s surface. Dump all this data in a geographic information system (GIS) and we can really start picking apart almost every up and down and slide and whatever comes along. Add high-powering computing to model the physical processes and the geosciences of 2018 would look like straight up science fiction to a geologist from 1975. Oh, but as that implies, it wasn’t always so good. Before this level of precision and accuracy in mapping the Earth’s surface, geoscientists had to rely on tools like optical leveling, tilt-meters and other more analog methods for seeing how the Earth’s surface might be changing. This is not to say that amazing maps weren’t made, but they took a lot of time and people-power to construct … and was we’ve found, they weren’t always right. That gets us to the Palmdale Bulge. Part of a 1975 USGS map showing the "Palmdale Bulge". USGS. Part of a 1975 USGS map showing the “Palmdale Bulge”. USGS. Back in the mid-1970’s, the Palmdale Bulge was all the rage, but even today, no one is quite sure if it was even real. It was a supposedly an uplift near Palmdale near Los Angeles where over sometime in the late 1960’s and early 70’s, the land rose 30-45 centimeters (11-17 inches). That is a lot of movement for what might have been only 5-8 years of change. The “bulge” appeared to cover almost 83,000 square kilometers (~32,000 square miles) of real estate. Since the whole Los Angeles area is criss-crossed with faults related to the San Andreas fault system, it was thought that maybe this uplift was a sign that a huge earthquake was going to happen … and soon. A lot was riding whether the bulge was real as Los Angeles was growing and people lived in the area. Evidence of a big earthquake in the works would cause real estate values to plummet. So, these finding were carefully scrutinized and the closer geologists looked, the more it seemed like something wasn’t right with the bulge. 'Leveling at the Washington Monument.

The Palmdale Bulge: A Geo-Crisis That Likely Never Existed

Explore satellite imaging of the Earth and how new techniques reveal subtle changes in our planet's surface, including the Palmdale Bulge.

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