Radiocarbon Dating Helps Solve Mystery

You never know what you might find underneath a tree.

A recent storm in Ireland uprooted a 200 year-old tree and embedded in its roots was a human skeleton. You can read the article and see some excellent images by clicking the link below.

BBC News Article

Examination of the skeleton has determined it to be a male between 17 and 20 years of age. Though the specific circumstances of the death are not known, evidence shows that he met a violent death, with several stab wounds in the chest area and one on the left hand.

The interesting aspect from an earth science perspective is that the skeleton's age was determined using radiocarbon dating, the same type paleontologists rely on to determine the age of fossilized, preserved and frozen remains, such as dinosaur bones, mummies and woolly mammoths.

In this case radiocarbon analysis shows the burial took place  between 1030 and 1200 AD, approximately 900 years ago.

In earth science, we study a number of radiocarbon systems, such a uranium-lead or potassium - argon. These systems have long half lives and are most useful for dating older rocks.  In this case, given that the items to be dated were carbon based and far younger, the carbon-12 to carbon-14 system was the chosen tool.

Could Sahelanthropus Have Ever Stepped on a Trilobite?

A question arose in class the other day when several students noticed the fossilized trilobite tracks shown in the picture below. 

The question focused on whether or not the trilobite was older or younger than any prehistoric man, and in particular, whether or not it was older than sahelanthropus.

Could sahelanthropus have ever seen a live trilobite? Interacted with it? Stepped on one while wading in water near a beach? Even found one tasty?

The answer lies in the time frame of geologic history during which sahelanthropus  and the trilobites lived. A little research reveals that there was no overlap between the two.

Sahelanthropus lived during the Miocene epoch during the Cenozoic era of geologic time. That would have placed him/her at about 7 million years ago at the oldest. 

Trilobites, those  famous arthropods we all study in our introductory geology courses, lived during the Paleozoic and stretch from 544 million years to 248 million years ago. They actually became extinct during the mass of extinction that occurred  at the end of the Permian/Paleozoic era.

So, it is safe to say that sahelanthropus never did see a trilobite, certainly not a real live one. Perhaps sahelanthropus saw the fossilized version, but as one of our earliest ancestors and a near relative of the chimpanzee, he/she would really not have been aware of the significance of  the fossil.

When Sport meets Geology....in a Sinkhole of All Things

It isn't everyday that I get to combine the worlds of sport and geology, in a writing piece no less.

Well...today's  the day. The picture in the link below, from nesn.com, shows a fairly large sinkhole that just opened up at a Jack Nicklaus-designed Top of the Rock golf course near Branson, Missouri.

Sinkhole in Branson, Missouri

Sinkholes are a curious site to most. They rare in many areas, especially where the bedrock is highly resistant to erosion. However, in areas with underlying soft sediments, and/or unconsolidated materials, groundwater can easily go to work and dissolve pockets of the subsurface away.

The result is caverns that are hidden below thin layers of overburden. We usually don't know they exist until the roof (the ground we are walking or living on) collapses and leaves a gaping hole.

Many are filled with the water that has infiltrated the soft ground, ironically at times being the one thing that holds caverns up, and the deciding factor in their collapse when it leaves.

The geology of the eastern American states of Kentucky, Pennsylvania, and Missouri is highly prone to sinkholes. The bedrock is mostly composed of the easily dissolvable types of soft sediment, such as limestone, gypsum, and halite.

Geologists refer to this as "karst" and some will remember that karst type caves are the sites of the common icicle or mound growths -the stalactites and stalagmite accumulations of carbonate rock we see. 

This sinkhole is about 80 feet wide and 30 feet deep, an average size.

One thing's for sure, it's one hole that for golfers, will be hard to miss.

Active Volcanoes in Newfoundland?

As we were recently studying the geology of Newfoundland, someone wondered if we still had active volcanoes.

The short answer is no. All areas that once had them are now so geologically old that once active volcanic regions are long past their active states.

Having said that, a great portion of the central part of the island's crust was built by marine volcanism. Volcanic activity occurred during the Paleozoic about 475 million years ago when the ancient Iapetus Ocean closed and the collision of the African and North American plates led to the creation of the Appalachian Mountains.

This was initially an ocean-ocean collision, very similar to the present type of plate collision that is now forming the islands of Japan. The results were similar as well. Japan is an island arc complex and the same processes were once at work in forming what is now the volcanic portion of central Newfoundland.

Kidney Stones - Are They Rocks, Minerals?

The title says it all...

In some ways, yes. Kidney stones are actually salts and minerals that crystallize in the kidneys.

If small enough (usually less than 3mm), they can pass through the kidney then through the ureters and then on through the bladder and out of the body. If they are too large they will get stuck and hence serious pain will occur.

Like some of the minerals a study in Earth Systems, they do have a similar type of formation. They contain lots of calcium like calcite, and they also crystallize out of a liquid like the precipitates we see in chemical sedimentary rocks. 

Though they contain calcium, they don't usually bond with carbonate or sulfate ions. The most common type of ion they bond with is called the oxalate ion.

Crystallization of kidney stones depends mostly on the amount of acid and the amount of dissolved salts in the urinary tract. Having lots of fluid in the urinary tract would enable salts to stay to dissolved and pass through the body; more salts would crystallize out when a person is dehydrated than when they are hydrated.

So, drinking lots of fluids would guard against kidney stones. They are not good to have.

Some can be even as big as golf balls and are extremely painful.

Potholes - the Road Variety

A recent question came up the other day....

How do potholes form?

This is a good question as it relates directly to geology. We don't cover it specifically in Earth Systems but it does relate to several concepts in the course. It is covered directly in World Geography.

Potholes, the types we see often in our roads in springtime, are a result of physical weathering.

During the winter, water underneath the road freezes and expands giving a frost heaving or frost action effect. The result would be slightly bumpier road or at least areas where the surface would be raised and uneven.

This would leave the pavement more easily broken if it were contacted by the force of a snow plow for example. Over several rounds of snow clearing, the pavement would be more and more broken, starting as several small chips which would lead to wider and wider holes.

Once the pavement is broken and increased water runoff occurs during late winter and early spring, further erosion occur and deepens the hole leading to the types of potholes that cause so much damage to cars.

The pothole problem is quite common in Canadian cities. Here is a brief news story published recently by the CBC.

 CBC Story - Potholes

Of course, there are other types of potholes that form around river beds due to the swirling motion of pebbles as flowing water carries them, but that's a discussion for another post.

Experts at Your Disposal

There aren't a lot of geology related q/a blogs out there, at least not exclusively devoted. After a quick look, I did find one site that contained some very direct questions and answers.

The site is called allexperts, found at:

http://www.allexperts.com/el/Geology/

It offers a host of knowledgeable experts who not only give clear answers, but are also rated.

Extrusive - Intrusive or Plutonic - Volcanic

The title of the post comes from a simpler question....

What is the volcanic equivalent of granite?

The quick answer is rhyolite, but we need to understand why.

The main thing we need to start with is that granite is an igneous rock. Igneous rocks are originally born from the cooling of a melt.

If the melt cools below surface, this is an intrusive environment and the rock is considered plutonic.


If the melt makes it to surface, the environment is extrusive and the rock is volcanic.

The key thing to remember is that you can have the same mineral composition in a melt regardless whether it is plutonic or volcanic. The minerals will be the same but they will cool under different condition and the rocks will have different textures.

So...when a melt containing quartz, feldspar and biotite cools and solidifies in an intrusive environment, the rock is a granite. When it form in a volcanic environment, the rock is a rhyolite - same minerals, different environments.

Superposition

Let's start with one of the simpler concepts in geology...

What is superposition and why is it so important?

Superposition states that in a sequence of layered, horizontal beds (sometimes called strata), the oldest bed (layer) is on the bottom and the beds get younger as you move towards the top of the set.

The law of superposition was proposed by Nicolaus Steno just over 300 years ago.

Superposition assumes that the beds are undisturbed (were not overturned, for example).

It would also work for a series of lava flows that have been laid down, one atop the other in a similar horizontal sequence.

Superposition is an important and fundamental law because it helps determine the relative ages of rock layers.  It helps us determine the geologic history of an area.

Gotta Love Igneous

I had to resist giving this a title with some cheesy pun, such as "igneous rocks are hot." In fact, they actually are...in more ways than one.

We have recently started igneous rocks and have been exploring classification, based on texture and composition. The birth of extrusive rocks, such as basalt under water is spectacular.

The link below shows some footage filmed underwater on a lava dive near Hawaii. A classic piece starts at about 1:18.

Pillows Filmed Near Hawaii

Living in Newfoundland, many are surprised at the wide range of igneous rocks we have here. Granite and gabbro are quite common and well exposed. The potentially cooler aspect is that we have lots of volcanics too. Rhyolite and basalt also provide evidence of our volcanic past. We see some rhyolites in the western section of the Avalon zone, but it is in the central region (the Dunnage Zone) where ocean-ocean plate collision during the closing of the Iapetus Ocean gave rise to submarine volcanism.

The result is an abundance of pillow lavas which are now exposed in the central areas of the province, especially around the shorelines near the town of Springdale.

They look remarkably like those seen below, in a photo from Brittany, France.

Pillows most often appear in the rock record as above - a stack or mound like structure with individual pillows laying atop one another. Shapes are generally oval.

Given that many have escaping gas, vesicles are found mainly near the top. Likewise, they are convex on their top surface (probably due to bending over other pillows below). These guidelines, among others, are quite useful in determining the top and bottom of a sequence....pretty cool.