Friday, September 8, 2017

How Do You Explain Different Fossil Hominids Having The Same Age?

 How does geology figure in the study of hominids? Primarily in learning how old the fossils are and what the environment was like that that they lived in.

Q: Bill Nye once said, that if you ever have an example of a fossil ever being discovered in a layer of earth that is from a different era that it would change the way we think about evolution and would be monumental. Now I find the evidence that science produces is the most compelling of any other narrative that we have of the world past, present and future. However, to maintain the credibility and ethical integrity of logic and reason. You must question and if it doesn't fit you must discard the idea. So, the question is. How is it that in 1959 and 1960, the fossils of Zinjanthropus and Homo Habilis both dated at 1.8 million years be found in the same geological layer? The layer that Mary Leakey was walking on when she accidentally stumbled upon the missing link. Both were found away from dig sites so the earth wasn't excavated. Mr. Leakey was ill when he first laid his eyes on Zinj. Suppose he dropped dead right then and his body was never moved. Future diggers would find two 1.8 million year old skull fragments and that of Leakey's all in the same geological layer.
– Levi T

A: First, the fossil record for hominids is incredibly sparse. The precision of most age-dating technologies is also not as precise as numbers on a popular science graph might suggest. It is thus really stretching it to draw any age conclusions unless you have U/Pb or other dates directly from the bones. It is extremely rare, however, that you will find adequate (undisturbed) isotopic content to do reliable dating with fossilized hominid remains; this leaves you with dating the stratum they are found in. In east Africa there are a lot of volcanic ash deposits that are relatively easily dated. Thus, for instance, you can say that a fossil tooth was found between ash layer X and ash layer Y, which are both dated - so you can place the hominid between these two ages.

 Second, it is now known that different hominids (for example, Homo Erectus, Homo Habilis, and Homo Paranthropus) overlapped in time - they were on the same continent and perhaps even in direct physical contact during their range of existence.

Third, the nature of decomposition and fossilization are such that Louis Leakey would leave remains dramatically different than something 1.8 million years old.

Fourth, there is also a big difference between a conformable and an unconformable geologic contact. It's pretty obvious if something was buried at the time the sediments were forming vs afterwards. 

Tuesday, August 8, 2017

Is Yellowstone About to Blow?

If you’re being shot at, there is some satisfaction from knowing how often you are being shot at. This holds for volcanoes, even super volcanoes.The last time Yellowstone erupted it left a layer of ash over 20 meters (70 feet) thick some 1,200 kilometers (800 miles) away near Colorado Springs. I know, because I personally pulled a camel's tooth out of the base of the Pearlette Ash deposit there. This was not a trivial eruption, and ash from it has been found in drill-cores on the east coast of the US and in the Gulf of Mexico. It probably killed everything within 1,000 kilometers in all directions.

Q: Do geologists know when Yellowstone might erupt again? It appears to erupt every few hundred thousand years.

The first was: 2,100,000 years ago
Second was: 1,200,000 years ago
And the last one was: 640,000 years ago

Are we in any danger of a fourth one?
- Brandon F

A: Yes - we are very aware of this eruptive periodicity in the USGS Volcano Science Center - we have a full-time volcanologist assigned to Yellowstone as the Scientist-in-Charge (SIC) of the Yellowstone Volcano Observatory. He works in close coordination with seismologists at the University of Utah, and with the US Park Service. Some links might be of interest to you:
Most important from your point of view might be the Yellowstone hazard assessment:

Christiansen, R. L., Lowenstern, J. B., Smith, R. B., Heasler, H., Morgan, L. A., Nathenson, M., Mastin, L. G., Muffler, L. P. & Robinson, J. E. (2007). Preliminary Assessment of Volcanic and Hydrothermal Hazards in Yellowstone National Park and Vicinity. U.S. Geological Survey Open-File Report , 2007-1071, 98 p.
Rest assured that the caldera is closely monitored by several different entities including the USGS. Our experience is that, while you cannot predict an earthquake, you CAN predict a volcanic eruption if you have adequate instrumentation on the volcano. Several of our staff returned just this week from making our periodic gravity and geodetic GPS surveys (these will detect inflation, for instance). The caldera and surrounding terrane are very well-instrumented with telemetered seismometers, also.
The assessment of the SIC is that we are not likely to have a super-eruption in our lifetimes - that's essentially the assessment above. I will excerpt key pieces of it here for you:

"No volcanic eruption has occurred in Yellowstone National Park or vicinity in the last 70,000 years or more."

"One statistical measure of eruption probabilities based on this episodic behavior suggests an average recurrence of 20,000years. The fact that no such eruption has occurred for more than 70,000 years may mean that insufficient eruptible magma remains beneath the Yellowstone caldera to produce another large-volume lava flow."

Table 5. Estimates of annualized probability of events greater than a given magnitude.
Diameter (m)       Area (m2)    Events in last 14 thousand years     Annualized Probability
                >2                           3.1               7000 (estimated)                                   0.50
            >300                  70,700                      16                                                      0.0013
          >2000             3,140,000                        2                                                      0.00014

This last table is from page 83 of the report. The chances for a large hydrothermal eruption next year (NOT a super volcano eruption) is just a bit over 1 in 10,000. For reasons explained above, the probabilities are likely even lower than this.
Bottom line: those in the (detailed) know are not worried.

Friday, July 7, 2017

Where did this rock come from... and, uh... is it legal?

There are rock and mineral shows all over the world, and for a price you can acquire a gorgeous Trilobyte fossil, a stunning Epidote crystal, or a piece of a meteorite. However, if the vendor sells you something but is unwilling to provide its provenance - where it came from - it is probably wise to get suspicious. 

Kilauea volcano in Hawai'i is a case in point. It's a National Park, and it's illegal to take any volcanic sample unless you have a legitimate research permit (which the US Geological Survey has, but still uses only sparingly). Imagine if every tourist hauled away 5 kilos of lava. With hundreds of thousands of tourists over time this has a significant effect - causing visible damage to a National Park. The US Post Office at Volcano, Hawai'i, has a back yard pile of volcanic lava. They have all been mailed back by guilty people, after they surreptitiously collected a sample and took it back to Iowa... Hundreds to thousands of kilos of lava are returned each year. This may also have something to do with Pele's Curse - there are ubiquitous warnings that the volcano goddess Pele will curse anyone taking part of her away. When bad things happen to someone (bad things happen to everyone), then some people may feel it must be because they did something wrong. 

This problem is far worse with archeological sites and African wildlife. As a general rule, it's unwise to buy any archeological artifact, or any ivory, because the likelihood that it has been legally obtained is vanishingly small. Archeological looters - grave robbers - operate with different degrees of impunity all over the world. There are laws against looting burials in most countries, but they are difficult to enforce, and many ancient cemeteries are littered with crude potholes. Priceless information is lost this way - not to mention who wants their grave dug up for trinkets? It's not unlike the ongoing massacre of elephants and rhinos in Africa, done to satisfy the insatiable demand of wealthy clients in Asia and the Middle East. 

If you have doubts - then it's probably wrong.

Q: I just purchased a volcanic bomb that was from somewhere in Alaska. I'm trying to identify which volcano it may be from. Any idea on how to narrow possibilities. Its a lovely piece but my "organized self"  would like to put a label on it as to source... if possible. So far I have Mt. Aniakchak but assume it could be one of a number of choices.
- Frank S


The only reliable way to know the provenance of a rock sample is from the person you purchased it from. That, I would think, would be a minimum requirement to sell something like this. In the past I've bought Trilobites from Morocco, and several fragments of iron-nickel asteroids at rock and mineral shows (and a tiny piece of one Nakhlite from Mars), but I would not consider buying them if I didn't know where they were acquired - that's in part because I'm a geoscientist and want to understand things. However, it is also in part because I don't want to contribute to a serious looting problem:

There is the possibility that your volcanic bomb was acquired on federal land or private land that the seller couldn't legally poach from, and that may explain the reticence to provide a specific source. People who sell fossils, mineral samples, and meteorites at rock and mineral shows are always very careful to provide provenance as a way to protect themselves from prosecution. 

Generally, to provenance an unknown-source rock requires a careful comparative isotopic and petrographic analysis - this is how experts learned that the two-to-four-ton Preseli "bluestones" from the third construction phase Stonehenge came from Wales, 250 kilometers away, for instance.