Monday, October 30, 2023

Geology Through the Radio - A Horse With No Name



America's "A Horse With No Name" is one of my favorite examples of Geology Through the Radio, because it isn't what you would expect.


A Horse with No Name
On the first part of the journey
I was looking at all the life
There were plants and birds and rocks and things
There was sand and hills and rings

The first thing I met was a fly with a buzz
And the sky with no clouds
The heat was hot and the ground was dry
But the air was full of sound

I've been through the desert on a horse with no name
It felt good to be out of the rain
In the desert you can't remember your name
'Cause there ain't no one for to give you no pain
La la la la la la...

After two days in the desert sun
My skin began to turn red
And after three days in the desert fun
I was looking at a river bed
And the story it told of a river that flowed
Made me sad to think it was dead

You see I've been through the desert on a horse with no name
It felt good to be out of the rain
In the desert you can't remember your name
'Cause there ain't no one for to give you no pain
La la la la la la...

After nine days I let the horse run free
'Cause the desert had turned to sea
There were plants and birds and rocks and things
There was sand and hills and rings

The ocean is a desert with its life underground
And a perfect disguise above
Under the cities lies a heart made of ground
But the humans will give no love

You see I've been through the desert on a horse with no name
It felt good to be out of the rain
In the desert you can't remember your name
'Cause there ain't no one for to give you no pain
La la la la la la...

Geology
While not explicitly "geological", I have always found the lyrics in "A Horse With No Name" to be reminiscent of a major geological event. When looked at the course of the song, the rider starts off in the desert, however by the ninth day "the desert had turned to [the] sea". When a land surface that is subaerial eventually gets covered over with the ocean, this is known as a transgressive sequence

Figure 1: Transgressive sequence. Image courtesy of SEPM

As you can see in Figure 1 above, the desert/beach in Image A is eventually overrun by the ocean/sea in Image B. There are two possible methods for this to happen. One is that the land surface could be slowly sinking in relation to sea level. This can actually be witnessed today in areas along the coasts where the weight of the sediment, or even buildings, slowly lowers the surface elevation, such is in the case of New York City or Venice. The other is that sea level is rising in relation to the land surface. This can also be witness today with the continued melting of the polar glaciers due to climate change and a quickly warming planet, this melting ice can be seen to raise sea level over time. There is also a third possibility, which is a combination of the two events occurring. 

As the sea level rises in relation to the land and inundates the surface, eventually the sediment that is deposited will change. As we can see in Figure 1 above and Figure 2 below, the surface sediment for a desert or a beach would typically be sand. Once the land is inundated, that sand would shift to clay or mud as the water levels progressively got deeper and further away from the shoreline. Eventually the water would be deep enough with the shoreline far enough away that most sand and mud/clay would get deposited closer to shore, leaving only the deposits from the dead animal life as it built up over time. These dead organisms, formed mostly from calcite shells, would be compacted and lithified (turned into a rock), over time. These rocks are mostly a variety of limestone, which is identified by the blue brick pattern seen in the figures above and below. 

Figure 2: A simplified example of a transgressive sequence in the rock record. 

This pattern can also be seen in the rock record. If we were to see the rocks sitting on the side of the road, what is known as an outcrop (Figure 2), they would generally have the pattern of sandstone on the bottom representing the beach or desert. Siltstone above that, which is a smaller sediment size typical of the just offshore environment. Then mudstone or shale, a rock typically of fine layers of clay sized particles that is even further off shore. So in this instance as the water level deepens, the shoreline is shifting away from this location. And finally on top is the limestone, where we have reached a far enough distance from the shore that particle sediment (like sand and mud) is limited. 

There is one major point of interest between a real life transgressive sequence and the song, and that is a matter of time scale. A true transgressive sequence like this would typically take hundreds of thousands to millions of years to fully inundate a desert like environment, however in the song it only takes nine days. So, while it is a cool comparison to a real life geological event, it does need to be taken with a grain of salt. 


Possible Educational Questions to Ask
1. What are the environments mentioned in the song?

2. What types of conditions does the song use to define these environments?

3. Does this match what is geologically used to define the environments?

4. What did the singer of the song find on the 3rd day, and do you think you could see this feature in the desert? 

5. What is the geological term for the change in environment described in the song (“desert had turned to the sea”)?

6. What are the two (tectonic) possibilities to explain how this could happen?

7. The song states that “after 9 days…the desert had turned to sea”. Assuming a really fast time period for this to happen is 100,000 yrs. How much faster is this event that the band America described in the song?

8. “The ocean is a desert with its life underground”. Now assuming they meant underwater, do you agree with this statement? Why or why not?

You can see the rest of the Geology Through the Radio postings on my website.

Friday, October 20, 2023

Geology Through the Radio - Pompeii


One day I was listening to the radio and it a appeared that a geologically themed song was playing. Little did I realize when I first heard it, that the song title, "Pompeii" by Bastille, was also geologically themed. After that I proceeded to listen to the lyrics a bit more closely, I realized that not only was the song named after a geological event, it actually was completely about that said event (not some fancy title that has nothing to do with the song what-so-ever).


Here are a snippet of the lyrics for instance:
And the walls kept tumbling down 

In the city that we love 

Gray clouds roll over the hills 

Bringing darkness from above
The Geology

I found this song a perfect example of geology on the radio because they decided to title the song simple "Pompeii", which is a reference I am assuming a lot of people would get.  

For those who don't know, the song talks about the eruption of Mount Vesuvius back in 79 CE (Common Era), which destroyed the town of Pompeii. Along with Pompeii, the lesser known town of Herculaneum was also destroyed in the same eruption. 

The towns were destroyed during the release of volcanic ash, gas, pyroclastic debris, and eventually in what is called a pyroclastic flow. 
A pyroclastic flow off the side of Mount St. Helens, May 18, 1980. Image courtesy of the the USGS

A pyroclastic flow is a super heated (>400 degrees C) ball of gas, ash, and rock that flows down the side of a volcano at tremendous speed (~100 km/hr). It is estimated that the ~2,000 victims of the eruptions found at Pompeii were killed within 15 minutes of the eruption (The Guardian).  

In an interview about the song, the band's frontrunner Dan Smith (RadioX) said that: 
"I was reading a book that had some picture of the people who got caught up in the volcanic eruption. And it's just such a kind of dark powerful image, and it got me thinking about how boring it must have been emotionally after the event. To be sort of stuck in that same position for hundreds and hundreds of years. So, the song is sort of an imaginary conversation between these two people who are stuck next to each other in their sort of tragic death pose".
Cast of some of the victim's bodies at Pompeii. Image courtesy of the Global Volcanism Program

The victims of the eruption likely died in a multiple of ways. The first wave of deaths took place from the raining cloud of rocks from the initial eruption that Mt. Vesuvius ejected into the air. These rocks have been shown to have caused head traumas to many of the victims (The Atlantic). More deaths occurred from the suffocating ash and toxic gasses, and then eventually the pyroclastic flow. The ash adhered to the bodies of the victims, essentially cocooning them in a hardened shell of rock. Over the centuries the bodies decayed, leaving behind voids in the rock. It is these voids that archaeologists eventually realized formed something, so they filled them with plaster, only to discover that they were the remains of the victims. Unlike most of the organic material which decayed away, many of the bones also remained within the voids left behind in the ash. 

You can see the rest of the Geology Through the Radio postings on my website.