Invasive Species: Friends or Foes?

We’ve all heard horror stories about invasive species, but are introduced plants and animals really as bad as the media paints them?

News headlines on invasive species. Image by author. Sources for headlines.

The answer to this question depends on exactly which invasive species we are referring to.

The brown tree snake (Boiga irregularis) is an example of a truly harmful invasive species. 

Brown tree snake. Public domain image. Source.

The brown tree snake arrived on the small Pacific Island of Guam in the late 1940s or early 1950s as a stowaway on military cargo, and has since eaten most of Guam’s birds, lizards, and small mammals. Guam’s fauna never experienced predation by a large snake before, and they are suffering horribly under the reign of the invasive brown tree snake.

In addition to eating Guam’s native species, the brown tree snake causes frequent power outages. How can a snake cause power outages? By climbing pylons and shorting out the power circuits! Climbing pylons is a dangerous hobby as it kills the snake, inconveniences Guam’s citizens, and costs power companies too much money in repairs.

Brown tree snake on top of a fence post. Creative commons image. Source.

The brown tree snake also costs the US military stationed on Guam millions of dollars each year in safety measures to prevent this pesky predator from escaping to another island. So far, this money is well spent as the brown tree snake has not escaped Guam.

The only good thing about the brown tree snake is that it eats Guam’s rats.

But what about another invasive species, garlic mustard (Alliaria petiolata)? I remember when garlic mustard was one of the most hated plants in NYC. Garlic mustard grew in dense monocultures and drove out other plants. Every time I went on a walk I would see huge piles of garlic mustard the parks department ripped out of the soil in an attempt to eradicate this species. Now, I rarely see piles of dead garlic mustard. Instead, I see garlic mustard growing alongside other plants along the park paths. What caused this change?

Garlic mustard. Creative commons image. Source.

 Garlic mustard was deliberately introduced to the United States in 1868 on Long Island for its ability to control erosion and its medicinal properties. While garlic mustard may look innocent and charming with its little white flowers, this plant had serious issues with poisoning its neighbors. 

Sinigrin, the toxic chemical garlic mustard emits, kills nearby plants and mycorrhizal fungi. Mycorrhizal fungi are a type of fungi which colonize the roots of plants and help their plant partners absorb more water and nutrients. Without their mycorrhizal fungi, the lives of plants living near garlic mustard were jeopardized, which allowed garlic mustard to push these plants out. Soon garlic mustard was dominating the forest floor.

Now, garlic mustard has been living in the United States for a long time and it is learning to be a kinder neighbor. U.S. garlic mustard doesn’t emit as much sinigrin as it used to, and the plant can grow next to other species without killing them.

Garlic mustard flowers. Creative commons image. Source.

Why is this?

High levels of sinigrin release, seen when garlic mustard first was colonizing the states, is most beneficial for garlic mustard when the plant is mainly competing with other species. However, when garlic mustard is well established, it mainly competes with itself, which means low levels of sinigrin release are preferable. Low levels of sinigrin emission are currently so favorable for the U.S. garlic mustard population that the genetics of this population changed to make low levels sinigrin release widespread and innate.

Now that garlic mustard has had a chance to settle into its new home, it’s not acting particularly dangerous and invasive anymore, is it?

Purple loosestrife (Lythrum salicaria) and Canadian pondweed (Elodea canadensis) are two other introduced species, like garlic mustard, accused of forming monocultures and driving out native species. After forming dense stands during the first few years of introduction, purple loosestrife and Canadian pondweed populations both declined significantly, like garlic mustard did, and they now live peacefully next to native plants. Non-native species may need a few years to acclimate to their new homes. We may be accusing them of wrongdoing too quickly.

The purple haze in the background of this photo is purple loosestrife.
Photo by PBM. Used with permission.

Admittedly, garlic mustard, purple loosestrife, and Canadian pondweed are not the worst invasive species. These plants don’t hold a candle to the brown tree snake. Are the more wickedly painted invaders, like zebra mussels (Dreissena polymorpha) or tamarisk (Tamarix sp.), ever falsely accused?

News headline on invasive species. Image by author. Sources for headlines.

Yes, non-native species are often blamed for problems we humans caused simply because they are found near where the damage occurred. 

Illustration of a zebra mussel. A public domain image. Source.

Zebra mussels are incriminated for clogging pipes, covering every hard surface underwater, and eliminating endangered freshwater mollusks. The fact is, freshwater mollusks were on the decline long before zebra mussels ever arrived because of habitat degradation and pollution caused by humans. Zebra mussels do compete with these mollusks for food, but it is wrong to blame them for endangering the mollusks. 

Zebra mussels. Creative commons image. Source.

Zebra mussels do cover a large amount of hard surface area underwater, but while doing so, they filter polluted water. As a result of the zebra mussels’ filtering job, the water is clearer, which promotes the growth of aquatic plants. These plants provide cover for fish and invertebrates and help increase their populations. The fish then feed on the zebra mussels and help clear some of the hard surfaces they live on. Zebra mussels also serve as a major food source for waterfowl. 

Yes, zebra mussels may inconvenience water companies by clogging their pipes, but they aren’t the evil species the media makes them out to be.

Zebra mussels on water meter. Public domain image by NOAA. Source.

Tamarisk has a similar story. This small tree is blamed for being a water hog and for destroying native bird habitat. Actually, humans were the ones using all the water. Tamarisk use about the same amount of water as native plants. In addition, tamarisk provides habitat for native birds. This plant isn’t quite as bad as the headlines make it seem.

Tamarisk flowers. Creative commons image. Source.

The whole idea that introduced species must be harmful is a xenophobic attitude. Once a non-native species takes root, it is next to impossible to eradicate. Introduced species are not going away anytime soon either, as international trade and travel just make it easier for species to globe trot. It’s time to accept the innocent immigrants species and the benefits they can offer our ecosystem.

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The Brain on Coffee

I recently became a coffee drinker, and as I drank my coffee one morning, enjoying how much more awake and alert I felt with every sip, I began to wonder: why does coffee help me wake up and focus? What is caffeine doing to my brain?

Photo by History Underfoot, Used with permission.

Energized by my morning brew, I jumped right into research. Soon I learned many new words (neuroscience papers are superfluously verbose) and why coffee helps most of us feel more human on even the least promising morning.

A drawing of the brain.
A public domain image. Source.

The invigorating effect of coffee can be traced to the caffeine present in the beans. We all know that caffeine is a central nervous system stimulant. But how does it get into our nervous system in the first place? Caffeine can easily cross the blood brain barrier, a screening system which prevents most chemicals from entering the brain, to interact with our neurons. 

Stained neurons.
A creative commons image. Source.

What does that mean?

Before I explain exactly how caffeine interacts with our neurons let’s back up a little and briefly review how our brain works. Our brains are made of neurons which respond to stimulus by sending and receiving neurotransmitters. Neurotransmitters are chemical messages which either trigger neurons to release more neurotransmitters—or stop neurons from releasing more neurotransmitters. The complex patterns of releasing and withholding neurotransmitters are what allow us to move our muscles, to make decisions, and form memories.

A creative commons image. Source.

One end of a neuron—the end which receives neurotransmitters—is made of many branched extensions called dendrites. The dendrites are covered in receptors which interact neurotransmitters. Different types of receptors respond to different neurotransmitters. 

Now, let’s get back to the coffee. Caffeine mainly affects two types of receptors known as the A1 and A2A receptors. These receptors normally receive adenosine, a neurotransmitter which helps us sleep and relax. Caffeine blocks the A1 and A2A receptors and prevents them from receiving adenosine. With less adenosine interacting with our neurons we automatically feel more alert and awake. 

Drawing of neurons.
A public domain image. Source.

Caffeine,  in preventing adenosine from doing its job, has a few side effects like increasing anxiety. People who are prone to anxiety and panic attacks—and first-time coffee drinkers—are more likely to feel nervous after a cup.

Luckily for us regular coffee drinkers, most people’s brains habituate to caffeine very easily, and the caffeine jitters become less pronounced the more frequently one drinks coffee. After my first cup of coffee, I felt a little on edge, but now that I’ve been enjoying coffee daily for about two weeks, I don’t feel nervous after my morning mug.

Vintage coffee can.
A creative commons image. Source.

Caffeine promotes alertness, which is great during the day, but not as pleasant at bedtime. Even if one does manage to fall asleep after drinking coffee in the afternoon, caffeine reduces the amount of deep sleep per night and increases the amount of light sleep. The rapid eye movement (REM) sleep, or dreaming sleep, remains the same regardless of coffee consumption. First-time coffee drinkers are more likely to experience sleep disruption as increased caffeine tolerance reduces the drug’s influence on sleep.

Another thing I learned is exactly how quickly one becomes accustomed to caffeine depends largely on genetics. Some people’s livers metabolize coffee slowly, and since caffeine would remain in their bodies longer, it may have a stronger effect on them. In general, people of Asian and African descent tend to metabolize caffeine more slowly than those of European descent. 

Author's own image.

I have not gotten my DNA sequenced yet, but I’m guessing that my liver metabolizes caffeine fairly quickly because I quickly became habituated to caffeine and my ancestors were European.

Coffee has a few other side effects like excessive urine production, increase in systolic blood pressure, and dilation of the airways. I’ve read that drinking too much coffee can raise the blood pressure to dangerous levels in people with hypertension. (Always do your own research.)

Author's own image.

For people without hypertension or caffeine-induced anxiety, lifelong coffee drinking is suspected to delay the onset of cognitive decline, Parkinson’s disease, and diabetes. One recent study found that drinking coffee reduced the risk of brain tumors in Japanese populations. The benefits of coffee drinking tend to be more pronounced in women.

Unfortunately, these health benefits only apply to lifelong coffee drinkers. Starting to drink coffee as an older adult can possibly increase cognitive decline. People with Parkinson’s disease and diabetes who began to drink coffee after they were afflicted reported no change in their symptoms.

Even if coffee can’t change the symptoms of Parkinson’s or diabetes, it can improve one’s mood. Coffee paired with bread and blue light is one of the top mood improvers! I know next time I’m feeling down try this coffee, bread, and blue light strategy. (Where do I find blue lights?)

Coffee and bread, my breakfast this morning! Author's own image.

Happy coffee drinking to my fellow coffee lovers!

Inspired to learn more about coffee? Check out my post on my other blog, Totally Baroque, about 17th century men and women who couldn’t pass a day without the “drink which drove away drowsiness" here.

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Cemetery Series: The Cemetery Habitat

Cortland Rural Cemetery. Photo Credit to PBM.

Cemeteries are not just for the dead, but for the living. In fact, graveyards serve as safe havens for rare plants and animals. Tombstones in Britain are the only home of some species of endangered lichens. The Calvary Cemetery in north St. Louis, Missouri contains the last original prairie grasses in the area and is one of the few spaces where ground-nesting bees survive. The Weißensee Jewish Cemetery in Berlin is home to 608 species of wildlife including an arthropod (Agonum gracilipes) which was thought to be extinct. It’s not extinct! That little invertebrate has been living in a graveyard in the middle of Berlin.

The Trinity Church Cemetery. Photo by author.

Cemeteries are often the only fragments of natural habitat left in cities or areas dominated by agriculture. This makes graveyards vital to the survival of many species.

Author's own image.

The Trinity Church Cemetery. Photo by author.

Wildlife thrives in un-manicured cemeteries and in cemeteries with tombstones placed close together. At the Weißensee Jewish Cemetery mentioned above – the place that surprised scientists with the arthropod – most species are found in areas left to grow naturally. Closely-crammed tombstones provide hiding places for animals like foxes and coyotes. Tight spaces between grave monuments also makes it harder to remove sprouting plants, allowing them to grow and prosper.

Kings Chapel Burying Ground. Photo by Author.

Author's own image.

The flora and fauna in cemeteries provide data on many topics like conservation biology, species diversity, and climate change. Managers at some cemeteries embrace the wildlife found among the gravestones and host birdwatching programs or guided hikes through their land. One great example is the Cortland Rural Cemetery in Cortland, New York that offers a self-guided tour on the cemetery featuring the trees and lichen growing there.

Cortland Rural Cemetery. Photo Credit to PBM.

To learn more about cemeteries and science check out my previous posts: Cemetery Geology and Death and the Environment.

The Trinity Church Cemetery. Photo by author.

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Cemetery Series: Death and the Environment

Cortland Rural Cemetery. Photo credit to PBM.

I often think about the effect of my lifestyle and actions have on the environment, but one thing I do not often think about is my death and how it will impact the earth. Death is a natural process, and the earth easily takes it in stride, however, the way we humans take care of and dispose of cadavers can have a positive or negative impact on the earth.

The two most popular ways to dispose of human remains in the modern United States are traditional burial and cremation. Neither option is environmentally friendly. To understand why, let’s examine the processes involved in traditional burial and cremation.

Traditional Burial

If traditional burial, complete with an open casket funeral, is chosen, the deceased is first drained of all blood and pumped full of embalming fluid, which is mainly made of formaldehyde, to preserve the body for as long as possible. The cadaver is then made presentable for the funeral and placed in a casket made of varnished wood, metal, or plastic. Once the funeral is over, the body is laid to rest in a concrete vault in a nearby cemetery.

The procedure of traditional burial is largely centered on using chemicals to keep the body from decomposing for as long as possible. These chemicals, and products from the plastic used to make or coat coffins, leech into the soil where they can be absorbed by nearby plants and animals. The chemicals enter the groundwater, posing a threat to people who rely on well water for drinking. Over 750,000 gallons of formaldehyde enter the soil every year from embalmed corpses in the United States alone.

Formaldehyde does eventually decay, but it is not healthy to have 750,000 gallons of a known carcinogen released into the environment. Frequent exposure to formaldehyde during the embalming procedure puts funeral home employees at a higher risk of getting cancer. The effects of other chemicals in the coffins and burial vaults on the environment are largely unknown.

Cortland Rural Cemetery. Photo credit to PBM.

The idea of slowing down decomposition and preserving the body in an illusion of life promoted by traditional burial would make sense if the cadaver was being kept as a scientific specimen to be used for research. However, there is little point in preserving a body that will be left to rest permanently underground. Besides, without constant care it is impossible to stave off decomposition forever, even the most embalmed corpse will begin to decay after a while.

Slowing down decomposition is neither healthy nor safe. The World Health Organization (WHO) recommends disposing of cadavers in a way that will allow them to break down as quickly as possible, to reduce the risk of pathogens colonizing the corpse and leaking into the soil and groundwater.

Traditional coffins and vaults waste valuable resources like wood, concrete, and steel which could be put to more effective use. In the United States, 30 million board feet of wood, 1.6 million tons of concrete, and 90,000 tons of steel are used in traditional burials, never to be seen again.

Traditional burial is rarely required by law, expensive, wasteful, and pollutes the earth. I hope that as more options for body disposal become available traditional burial will become a thing of the past.

Cortland Rural Cemetery. Photo credit to PBM.

Cremation
Cremation is widely viewed as a “green” alternative to traditional burial, but is it actually earth-friendly? Not really.

Cremating a corpse correctly takes about one hour of intense heat, 1590-1797 degrees Fahrenheit (950 degrees Celsius). Maintaining this heat level takes a large amount of energy, often obtained from fossil fuels. During the combustion process, pollutants like carbon dioxide, carbon monoxide, soot, and trace metals such as highly toxic mercury from dental fillings are released into the atmosphere. Each body burned uses 28 gallons of fossil fuels, finite resources, and releases 540 pounds of carbon dioxide. This adds up, considering 912,000 cadavers are cremated each year in the United States. The ashes left after cremation are not harmful to the environment, but since they are devoid of any nutrients, they cannot be used to nourish future life.

There are ways to reduce the environmental impact of cremation, such as choosing crematoria with scrubbers or filters which help prevent pollutants from entering the atmosphere, wrapping the body in a natural shroud to make sure no excess chemicals are released as the shroud burns, removing dental fillings and medical implants before cremation to prevent release of trace chemicals, and using a biodegradable urn if the ashes will be buried. Some crematoria donate to the carbon fund, an organization which works to reduce pollution and conserve nature, but are there ways to avoid producing pollution in the first place? Fortunately—yes.

Cortland Rural Cemetery. Photo credit to PBM.

Green Burial

Green burial is less of a new earth-friendly fad and more of a return to burial practices before embalming and concrete vaults existed. During green burial, the body is simply buried in a biodegradable coffin or shroud without any invasive chemicals. After being laid to rest, the corpse naturally decomposes and nourishes the earth. Some traditional cemeteries have a section dedicated to green burial, but there are other burial grounds which only accept chemical free bodies and shrouds/coffins. A few green cemeteries allow headstones that lay flat to the ground, while other cemeteries serve as nature preserves and no grave markers are allowed at all. In those places, graves can be found by GPS.  Some states allow people to conduct funerals in their own homes and conduct green burials on their own property, but the laws on this practice vary considerably by locality.

Green burial is cheaper than traditional burial because no expensive supplies or chemicals are used. One downfall of green burial is that it requires lots of open space, which is generally not available to city dwellers.

Composting Cadavers
Someday city inhabitants may have their own form of green burial consisting of specialized buildings for composting cadavers. The fertile soil produced by these facilities could later be used as a fertilizer for flower gardens. Similar to green burial, body composting will not release greenhouse gases or chemicals. Currently, composting corpses is not available to humans, though farmers commonly compost their deceased livestock.

Promession and Alkaline Hydrolysis

Promession and alkaline hydrolysis are two methods of body disposal that are advertised as being good for the environment, though an in-depth analysis of their effects on the earth has yet to be conducted.

Promession is similar in concept to green burial or urban composting, except the body is reduced to small organic fragments by a treatment with liquid nitrogen before being buried. Like the body composting, promession is not yet available to customers.

Cortland Rural Cemetery. Photo credit to PBM.

Alkaline hydrolysis, however is available in a few facilities in the United States. Alkaline hydrolysis, also called green cremation, is a process where the body is reduced to a sterile fluid and some bone fragments, using an alkaline solution of water and potassium hydroxide. Instead of slowing down the decomposition process as embalming does, alkaline hydrolysis speeds it up. Alkaline hydrolysis uses one-eighth of the amount of energy that cremation does and it does not release trace metals or greenhouse gases into the environment. The leftover bone fragments can be buried or scattered, similar to the ashes left over after cremation.

Donate to Science

Donating one’s body to science may not be environmentally friendly in the same way green burial or body composting is, but cadaver donations help researchers in a variety of ways from teaching anatomy to students, studying how bodies decompose, to research projects like testing safe seatbelts and airbags for new car models.

Filling out an application before death and going to a medical evaluation session are necessary steps for those who wish to donate their bodies. Body donation is by far the cheapest option of body disposal, in fact it is completely free. Once a cadaver is successfully donated, the family of the deceased has no control over what research project their loved one will participate in. The family will later receive ashes of the deceased and a letter naming the project their loved one was involved in.

Body donation is not for everyone, but the donated corpses provide vital resources for scientists. It is difficult to judge the environmental impact of body donation because the corpses are used in a wide variety of ways. However the cadavers are being used to

expand our knowledge, which is valuable to our society.

Burial at Sea

Full-body burial at sea is a lesser-known option that helps the environment by saving land for other uses. If the body is wrapped in biodegradable material, as required by most providers of sea burial, then the body can decompose naturally, with little environmental impact.

Cremated remains can also be put to good use underwater by becoming building materials for reef reconstruction technology.

Cortland Rural Cemetery. Photo credit to PBM.

These are just a few of the popular and earth-friendly options for body disposal. There are many other more eccentric options such as cryonics, mummification, shooting one’s ashes into space, or transforming the carbon in one’s body into a diamond. Though interesting, these options do not benefit the earth and are highly expensive.

For more on cemeteries and the environment keep an eye out for my next blog post in the Cemetery Series: The Cemetery Habitat.

Note: Flowers

Cut flowers, popular at funerals, are often grown in overseas in countries with poorly enforced environmental policies or no environmental policies at all. A whole slew of chemicals are used to grow these flowers, including DDT, which is illegal in the United States. These chemicals harm workers in the flower industry and the wildlife around the greenhouse where they are grown. Employees in these greenhouses are not only exposed to dangerous chemicals, but start working at a young age for long hours and have very few rights. The transportation required to ship these flowers across the world uses resources like fuel and releases greenhouse gases. It is possible to still have nice flowers and avoid contributing to the environmental harm by buying organic or fair trade flowers.

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Cemetery Series: Cemetery Geology

Cortland Rural Cemetery. Photo credit to PBM.

Cemeteries serve as memorials to our loved one’s lives and stories, but the stories of those who have passed on aren’t the only ones that can be found in a graveyard. Tales of geology, environmental health, and wildlife are also hidden there. Today I’m going to share some of the geological stories of headstones.

Kings Chapel Burying Ground. Photo by author.

Author's image.

Here are a few popular stones used in cemeteries over the centuries.

Granite

Granite. A creative commons image.

Granite is a durable igneous rock that makes for a long lasting tombstone. People began to use granite for cemetery monuments in the 1860s and it remains a popular stone for memorials to this day. Granite is formed from magma which cooled about ten miles below the earth’s surface. Whenever granite shows up at the surface of the earth that means the ten miles of earth covering it have eroded away over time leaving the granite visible. North Carolina is home to the world’s largest open-faced granite quarry. All stone there is mined directly from the surface. Granite comes in a variety of consistencies and colors determined by the composition of the minerals in the rock. Quartz, mica, and various feldspars make up most of granite and give it a characteristic speckled look. Sometimes granite contains xenoliths, sections of foreign rocks which did not melt and integrate into granite smoothly, but remained their own species of rock.

Granite holds up well under weathering, though the mica in it may degrade leaving it pitted. Stains from soot can darken granite, and lichens, moss, and ivy growing on the stone can change its appearance as well.

Quincy Granite Scandal

In the 19th century a dark variety of granite found near Boston known as Quincy granite was all the rage. Quincy granite got its dark color from some of its feldspars which were degrading into clay in a process called kaolinization. Quincy granite was used in many buildings and monuments until people found out that much of the stone being sold wasn’t actually Quincy granite at all, but a lighter granite rubbed with carbon and oil to make it darker. This dye eventually faded, leaving the stones splotchy and the customers disgruntled. After this scam no one wanted anything to do with Quincy granite.

Sandstone

Prepared sandstone sample. A public domain image.

While granite (non-dyed) holds up well under weathering, sandstone is probably the least durable rock used in cemeteries. Whole layers easily flake off as wind and rain wear down the stone. Monuments and headstones made from sandstone were popular from 1650-1890.

Monument at Cortland Rural Cemetery. Photo credit to PBM.

Sandstone is a sedimentary rock formed from sandy broken up pieces of other rocks deposited at the bottom of a river or sea. When these deposits were subjected to intense pressure, they condensed into a new rock, sandstone. The color of sandstone differs widely across sandstone species depending on where they formed and how they weathered. Sandstone is often striped with different colored sediment. In addition to miscellaneous rock pieces, sandstone often contains quartz and feldspar, and is held together by silica, calcite, or iron oxides.

Limestone

Limestone quarry. A creative commons image.

Limestone is similar to sandstone, but it holds up to weathering better and it is formed from calcite and silicate sediment, not sand. Impurities in the sediment will create darker limestone, but lighter varieties with fewer impurities are the most prized. The calcite and silicate either directly precipitate from the seawater or are obtained from the abandoned shells of sea creatures lying on the ocean floor. Some limestone contains fossils of these organisms. Limestone commonly forms in tropical or subtropical seas where calcite and silicate are abundant.

Monument at Cortland Rural Cemetery. Photo credit to PBM.

Most calcite and silicate sediments are compressed into limestone in the same way sand is compressed into sandstone. Some limestones even contain visible sedimentary layers like sandstone does. However, oolitic limestone, also used for headstones, forms in a different way and doesn’t contain these layers. Small grains of sand roll about the sea floor collecting calcite, which acts as a matrix to bind these grains together, and voilà, oolitic limestone is formed.

Ooids in a thin-section. A public domain image. 

Headstones made of limestone were most popular from 1780-1930, but limestone was used much earlier to make the first sarcophagi. Sarcophagus literally means “flesh eat,” a rather disturbing name which stems from the unusual limestone used to make sarcophagi which ate away at human flesh.

Sarcophagus of Pharaoh Merenptah. A creative commons image.

Marble

 Marble. A creative commons image.

After limestone is metamorphosized at high temperatures and pressures it becomes marble. The purest marble is perfectly white and has a sugary texture. Marble is highly sought after for its elegant beauty. Marble may be beautiful, but over time its glory fades as carbonization brought on by rainfall causes its surface to recede, rendering headstone inscriptions illegible. In an effort to combat the lost lettering, lead letters were attached with pins to marble monuments, but eventually surface recession caused these letters to fall out. Marble is also easily stained with lichens or soot.

Author's own image.

Marble was in vogue from 1780-1930. The world’s most prized marble has no impurities and comes from Carrara, Italy. Michelangelo used Carrara marble to carve his famous statue of David, and Leonardo Da Vinci helped a quarrying machine for this site. Today, the supply of Carrara marble is running low. Oddly enough, the world’s cheapest marble, Italian grey marble, also hails from Carrara.

Monument from Cortland Rural Cemetery. Photo credit to PBM.

The United States contains several marble sources on the east coast, the most popular sites are Barre, Vermont and Knoxville, Tennessee. The land which now forms Vermont and Tennessee was once the bottom of a tropical sea, which provided the right conditions for limestone formation. This limestone then metamorphosized into marble. 

Monument from Cortland Rural Cemetery. Photo credit to PBM.

Slate

Slate. A public domain image.

Slate, like marble, is sedimentary rock that was metamorphosized to become a new variety of stone. Unlike marble, slate is formed from sedimentary rock made of mud and possibly volcanic ash, not limestone. Slate tends to be dark grey or tinted deep purple or green from the volcanic ash. It is layered in thin sheets that peel apart easily. Gravestones made of slate are often coated with a protective material to prevent water from getting between the layers and pushing them apart. Once the coating is on, slate weathers well given its hard nature. Being hard isn’t always good for a gravestone, however, as it is highly difficult to carve inscriptions into slate. Still, professional gravestone carvers in the later 1600s and early 1700s made impressive carvings on slate of death imagery such as skulls, hourglasses and cherubs. Carved slate gravestones in New England are a crucial relics of Puritan art.

Carved slate gravestone from King's Chapel Burying Ground. Photo by author.

Carved slate gravestone from King's Chapel Burying Ground. Photo by author.

Judge Hathorne's grave. Salem, MA. Photo by author.

Modern Additions

Larvikite and Gabbro are the most common stones used to make grave markers.

Larvikite. A public domain image.

Larvikite is a coarse grained igneous rock with an abundance of feldspars, which give it an iridescent shine. Most larvikite is mined in Scandinavia. It is still unclear how larvikite will weather since most gravestones made of it haven’t been up very long.

Gabbro. A public domain image.

Gabbro is also an igneous rock that appears dark grey, but turns black with polish. Molten black and white feldspars form this rock, which weathers easily when exposed to water. Gabbro is often mistaken for, and even sold as, black granite. One beautiful variety of Gabbro, black galaxy, is flecked with bronzite which gives the stone the aura of a starry sky at night.

Gravestones and monuments help us to honor our loved ones and give cemeteries their characteristic beauty. But how do these stones and what’s underneath them impact the world around them? Stay tuned for the next installment of the Cemetery Series: Death and the Environment.

Monument at Cortland Rural Cemetery. Photo credit to PBM.

Note:
In this post I used the terms gravestone, headstone, grave marker and tombstone interchangeably. By common usage, all refer to some type of burial marker. However, gravestones, headstones, grave markers, and tombstones actually are specific terms which refer to different styles of burial markers. Here is a link to a page which explains the exact definition of these terms for those who are interested. 

Sources.