Monthly Archives: January 2014

Remembering Challenger: 28 Years


It's been 28 years since the Space Shuttle Challenger (STS-51-L) broke apart just over a minute after launch.  Disasters like Challenger and Columbia remind us that space exploration really is a complicated and risky business.  Should we stop because something is risky? Absolutely not, but we should also not let such things become routine and fall out of the public view.

Remembering the Challenger Crew

The NASA family lost seven of its own on the morning of Jan. 28, 1986, when a booster engine failed, causing the Shuttle Challenger to break apart just 73 seconds after launch.

In this photo from Jan. 9, 1986, the Challenger crew takes a break during countdown training at NASA's Kennedy Space Center. Left to right are Teacher-in-Space payload specialist Sharon Christa McAuliffe; payload specialist Gregory Jarvis; and astronauts Judith A. Resnik, mission specialist; Francis R. (Dick) Scobee, mission commander; Ronald E. McNair, mission specialist; Mike J. Smith, pilot; and Ellison S. Onizuka, mission specialist.


AGU Education Demonstrations

I recently got back from the American Geophysical Union meeting in San Francisco and wanted to try out adding some videos to the blog. The education section had a poster session during the last day of the conference that was on collection of data in real time in the classroom. Some of the demonstrations were very interesting and I thought it would be fun to share here. I didn't have my good HD camera at the conference, but I did have my iPhone.

That being said these are rather rough videos. If you think these are interesting be sure to say so and I'll try to take some better camera gear to conferences!

Demo 1: Mantle Convection

Using a set of cross driven PVC rollers Gary Glesener (UCLA) demonstrated a basic, historical plate tectonic model with his classroom Griggs apparatus. I got most of the explanation and demonstration on video.

Demo 2: Internal Waves

This demo used a small tank with saline water in the bottom and a layer of fresh water floating on top to demonstrate the standing waves setup at the density contrast. Then with two conductivity probes they show the passing wave and phase offset to allow students to calculate quantities such as the Brunt–Väisälä number. Again I think that most of the explanation is on the video. This is one of many demos from Dr. Jonathan Aurnou's group at the UCLA SpinLab.

Demo 3: The Geodynamo

The last demonstration was very interesting, but sadly I only have the explanation on video. Luckily I have video of a similar apparatus I built years ago to supplement! The idea was to show how rotating fluids in the Earth can create our geomagnetic field. That is rather difficult to show, but the inverse is pretty easy. It is also the basis for magneto-hydrodynamic propulsion. Below is the video of the project being explained and a video of my apparatus from many years ago. This is another UCLA SpinLab demo!

My old version of a similar idea:


UCLA Modeling Educational and Demonstrations Laboratory
SpinLab YouTube Channel
SpinLab Webpage


20 Years Since Northridge


Today marks 20 years since the famous Mw 6.7 Northridge earthquake.  In the early morning hours the earthquake hit the San Fernando Valley region of California and caused massive destruction.  In the 20 seconds of shaking there were around 60 deaths and over 8,700 injuries.

While the magnitude is strong, it really isn't that impressive.  What is impressive about this event is the accelerations and velocities involved.  The ground acceleration was up to 1.8g (~54 feet/second^2) and the peak ground velocity was the highest ever recorded at just over 6 feet/second (1.83m/s)!

Without going into all the details of the earthquake that are easily available, I would rather provide a news clip of the evening after the event and ask a question.  If you live in an earthquake prone region, do you have a disaster plan?

As you can see in the video, when gas mains are snapped and fires start there are only minutes to evacuate.  Take some time and put together a survival bag as well as talk to your family (especially children) about what to do during a disaster.  Even if you don't live in an area with significant earthquake hazard this is important to do with the upcoming severe weather season.  Some helpful links are provided at the bottom!


American Red Cross Survival Kit Survival Kit
CDC Earthquake Health Information
FEMA  Earthquake Information
Earthquake Safety at Work

Exploding Ice and Rock - Booms Heard a Result of "Cryoseisms"

Ice Hanging From Rock

UPDATE 1/13/14: Frost-quake creates 100ft long crack here.

Over the past few days (starting around Christmas eve), there have been reports of large booming sounds associated with minor ground shaking across the northern states, as well as in Canada.  The Toronto events have a nice string of tweets that are associated with them as well.  Are these really explosions? Earthquakes? Sonic booms? The truth, as it turns out, is a rare event that produces what are known as "cryoseisms".  Oddly enough, these "frostquakes", as they are commonly known, have been discussed in the literature since about 1818!  Having a background in both meteorology and geophysics, cryoseisms are just one example of how closely related to two fields are.

So, what happens to produce such loud and potentially startling events? It's all about ice.  Cryoseisms occur when there are seasonal frost conditions, no insulating blanket of snow, lots of rain/thaw to saturate the ground, and a sharp drop in temperature.

Surface water penetrates into sufficiently permeable soil/rocks, but then is rapidly frozen with a fast drop in surface temperature.  Normally temperature drops slowly enough that the ice gradually freezes, giving the surrounding soil/rock time to adjust.  When really fast temperature drops occur and freezing is rapid, the surrounding areas are stressed by the expanding force of the ice.

The freezing process is actually a very powerful mechanism, and is one of the geologist's favorite ways to explain physical weathering of large boulders.  Freeze/thaw cycling has even been used as a quarrying technique in granite!

Expansion during this rapid freezing of infiltrated ground water stores energy in the surrounding rock/soil, like a spring, until..... BAM! Failure occurs in much the same way faults fail.  Here the driving force isn't tectonic though.

Cryoseisms can do light damage to structures in the immediate vicinity, but their intensity falls off very quickly with distance.  For the seismology buffs out there, the zero focal depth produces lots of surface waves, but these events are generally not recorded on seismic networks.

Want to know more about cryoseisms? The literature isn't too robust, but check out Barosh (2000), Nikonov (2010), and Voss & Herrmann (1980) for some starting points!

*Cryoseism is also used to refer to earthquakes at the base of glaciers as well.  That's a whole other story for another day!