Safe Places

Here is my research...

Hazard Maps

Briefly: This one's for you dad. Too bad it doesn't include winter hazards.

Earthquakes 101

There seems to be some confusion about earthquakes, and our associated risks with them. It is easy to watch the news and see the devistation that takes place somewhere else in the world, and worry that it will happen in our own backyard. If you live on the west coast, namely southern california, this may be very true, but for those of us elsewhere this may or may not be the case.

How an earthquake happens:

Simplistically, an earthquake happens when two large rocks slide past each other. This suture between the two rocks is called a fault. Faults range in size from a meter, to hundereds even thousands of kilometers in legnth. What causes an earthquake? It is when pressure builds up between the rocks and something gives suddenly. The point at where this happens is called the hypocenter. Often, earthquakes happen deep underground. Today's earthquake in Chile took place 60 km under the earth. The term epicenter refers to the location on the surface abouve the hypocenter. Kinda like "x marks the spot", and the earthquake itself is the treasure.

Am I at risk for an earthquake?


Well, here is a earthquake hazard map for the US. You be the judge.

With regards to todays earthquake in Chile, and any potential hazard that me and my family has by living in Phoenix:

When an earthquake happens, there are 2 types of seismic waves generated. The first is called a P wave. it is compressional much like sound is going through air. This however travels through the earth and speeds much faster than sound though. the 2nd type and the dangerous type is called a S wave. It is like the kind of wave where you make a wave in a streched out rope or wire. It is dangerous because of it's shear. it moves from side to side, and that what causes the damage. S waves dissapate quickly (see the USGS shake map), the p waves traveled from chile to both AZ an NH in about 20 minutes, then reverberated inside the earth for about 4 hours. The seismogram reading is essentially like putting a microphone in the earth and listening to it grumble. This earthquake, because of its magnitude, was a loud grumble. There are quiet grumbles too, like mining explosions, or large trucks driving near the seismogram.

Hopefully this all helps.

Magnitude 7.7 Earthquake in Chile

Holy cow, this one is HUGE. Here is a shot of a seismogram here in Arizona. This is how much shaking we have had!


Here is another seismogram reading about 2 hours later, its still going!


Let me give you some background so you know kinda what you are looking at. This is a seismogram readout from a seismometer located in Tucson. It records shaking in the earth. Most of the readouts on this machine are totally unfelt be humans, but the sensitivity of the machine is such that it picks up vibrational waves as they pass by. The earthquake was powerful enough in Chile to be very strongly noticed by the machines. There is resonant readings as the waves reflect within the earth. Kinda like when you splash in a pool of water. Although you might not be right next to someone who is splashing, you can see waves caused by it go by, and then as the waves reflect off the sides of the pool and go by again.

Here is an intensity map of the earthquake from the USGS:

Fossils

Due to an overwhelming response, here is my fossil collection:


This first photo is a collection of crinoid stems in a piece of weathered Redwall Limestone. The crinoid heads are missing, but the stems are nicely preserved because of their calcium carbonate pieces. those guys are about 335 million years old. The limestone that they are found in is one of the larger rock layers found at the Grand Canyon.

This next photo is a storm segment from the Naco formation. There are a least 3 different types of fossils in this piece. Can you find them? The twig looking ones are fossilized bryozoan, a moss-like creature. There are also crinoid stem segments, and a couple of clam-like shells






This picture shows an assortment of other fossils also from the Naco formation. There are (from left to right) a couple of clam-like fossils, crinoid stem segments, saved entirely in 3D (the little barrel shaped guys), a streched spiral gastropod (found in the Upper Iowa River neah Decorah, IA), and a few intact brachiopods. The difference between the brachiopods and the clam like ones is that the clam like ones (they have a technical name but i cant seem to remember what it is) are symmetrical through the suture, and the brachiopods' symmetry is perpendicular to the suture line. Here is a close up of the clam like ones...

Papago Park

I visited another local park here in Phoenix today. Its called Papago (pap-a-go) Park. It is located not far from ASU, but has some very interesting geology.

This perticular butte is fascinating to many people for mostly non-geological reasons. It has a hole in it that when standing in offers spectacular vistas of downtown. Anyway, the history of the rock. Formed at the same time as Hayden Butte, Hole-in-the-rock (thats actually its proper name) is formed from totally different processes. 17 million years ago, somewhere within 2 km or so, there once stood a mountain fromed from granite and quartzite. One very violent day there was a massive landslide that came off the mountain and headed toward an ancient river. The landslice eventually became lithofied (turned into stone) and formed the butte. Interesting enough, the mountain that formed the landslide had eroded completely and cannot be found anymore. The butte is composed out of a composite sedimentary rock called breccia (bretch-a) which is an amalgamation of mud, sand , and broken up parts of granite and quatrzite (all of which came from the parent mountain) some of the chunks of granite are as large as a house.

The holes in the rock were formed when these boulders fell out of the breccia, and then were exposed to what is called cavernous erosion. This erosion over the course of millions of years formed the caves that so many people enjoy today. On an even more interesting note, this butte has the Great Unconformity running right through it! Remember from my trip up to payson, how where was the section of 1.2 billion years missing. Well that same gap exists at the base of the butte. The base of the butte is made up of granite that is 1.8 billion years old (as old as the oldest rocks found at the bottom of the Grand Canyon). however i found a xenolith of some kinda ash metamorphic that is even older. I had to take a sample of that back for my collection (as oldest rock)

Payson

Yesterday we took a great field trip to see some cool rocks about 2.5 hours north east of Phoenix. These rocks are at the southwestern edge of what is called the Matzatzal Province. The Matzatzal province is the oldest rocks layer found in Arizona, ranging between 1.6-1.8 Ga, this layer is represented in the Grand Canyon as Vishnu Schist.

Here at stop #1, you can see the basement rock layer for our study, the Payson granite. The layer right above the granite is the Tapeats Sandstone (also represented at the GC). Whats amazing here is what is called the great unconformity. To the untrained eye, theese rock layers look like a normal transition, or juust like the same rock alltogether. But the bottom layer is 1.2 billion years older than the top layer (540 million years old.) What this means is that there is 1.2 billion years of rock history that is entirely gone.

Here is one of my professors (Dr. Stump) explaining some of the finer details of the strata (strata means column of rocks).
Here is another shot of the rocks:


A little farther up the section we came to the disconformity between the Redwall Limestone and the Naco Formation. The Naco is the layer on the top of the road-cut, whilst the Redwall is the bottom layers:

Here are some other views of the two groups. Can you see the division??


The Naco formation is LOADED with fossils! We took 60 minutes to sample and log some (which we also got to keep for our personal collections) I found about 30 or so in that time. Ranging from crinoids to brachiopods, there were some sweet samples! Ask me sometime and I'll post close-up's of the different ones. I also founs a cool sample that has criniods, brachiopods and fossilized bryozoans. These fossils are all form the Pennsylvanian period so they are about 300 million years old.
Here is a scenery shot of what the forests look like up there:

Here is a self portrait of me as I an taking notes:





There are more scenery shots. One of them is our group sitting at the top of the main section of Coconino Sandstone.
Here is one last shot of the group hiking to a remote locaton to look at a sample of the Apache Group formation, and then the Apache Group Formation itself.