New Technology For Dating Ancient Rock Paintings

A new dating method finally is allowing archaeologists to incorporate rock paintings — some of the most mysterious and personalized remnants of ancient cultures — into the tapestry of evidence used to study life in prehistoric times. 

---

In the study, Marvin W. Rowe points out that rock paintings, or pictographs, are among the most difficult archaeological artifacts to date. They lack the high levels of organic material needed to assess a pictograph's age using radiocarbon dating, the standard archaeological technique for more than a half-century.
Rowe describes a new, highly sensitive dating method, called accelerator mass spectrometry, that requires only 0.05 milligrams of carbon (the weight of 50 specks of dust). That's much less than the several grams of carbon needed with radiocarbon dating.
The research included analyzing pictographs from numerous countries over a span of 15 years. It validates the method and allows rock painting to join bones, pottery and other artifacts that tell secrets of ancient societies, Rowe said. "Because of the prior lack of methods for dating rock art, archaeologists had almost completely ignored it before the 1990s," he explained. "But with the ability to obtain reliable radiocarbon dates on pictographs, archaeologists have now begun to incorporate rock art into a broader study that includes other cultural remains.

Cave painting by the San people depicting an elephant hunt in South Africa. (Credit: iStockphoto/Gary Bedell)

Why Ancient Mayan Communities Were 'Living on the Edge' of What Is Now a Massive Wetland

ScienceDaily (Apr. 18, 2011) — University of Cincinnati research is investigating why a highly sophisticated civilization decided to build large, bustling cities next to what is essentially swampland. The research by UC Geography Professor Nicholas Dunning, a three-year, interdisciplinary project including David Lentz, professor of biological sciences, and Vern Scarborough, professor of anthropology, will be presented April 1 at the annual meeting of the Society for American Archaeology in Sacramento, Calif.

---

Dunning's research zeroes in on why larger and successful Maya communities were located along the edges of the massive wetlands of Tikal.
Supported by the National Science Foundation and the Wenner Gren Foundation, the UC researchers are exploring different aspects of the ancient Maya in one of the premier cities of the ancient Maya world, Tikal, located in northern Guatemala. It's a region where architecture -- pyramids, palaces and temples dating as far back as the fourth century B.C.- are still standing in tribute to this ancient, sophisticated, Native American society that largely disintegrated around 900 A.D. Their demise has remained a mystery for centuries.
Located near the southwestern margin of the Bajo de Sante Fe, it's also a challenging region to conduct research. "It doesn't take a lot of rain to make it impossible to get in and out of the bajos. They're seasonal swamps. The mud gets deep very quickly," explains Dunning.
But the researchers have found that when the Maya started building their cities adjacent to these wetlands, they were different environments than what exist now, Dunning says. Portions of the area where UC researchers are working once may have been a shallow lake and perennial wetlands from which early populations extracted organic, peat moss-like soil to help sustain nearby fields where the Maya were primarily farming maize. Over the years, the farming-on-the-edge practice on sloping land led to soil erosion that resulted in creating aprons of deep, rich soil along the interface between the uplands and the swamps.
"We have good evidence from Tikal and other sites in this region that these areas became the focal point where agriculture occurred in the Classic Period, where these anthropogenic soils were created at the base of the slopes," Dunning says.
In regard to the edge farming, the researchers studied the soil and found significant amounts of pollen, which would indicate a significant amount of maize was produced. In addition, the organic matter produced from the corn was reflected in the soil's composition.
The UC research was a joint project with Instituto de Antropología e Historía (de Guatemala) -- IDEAH -- under the Guatemalan government. Lentz and Scarborough will also be presenting findings related to their fields -- regarding the Maya's advances in forestry and water management -- at the conference.
Dunning has been conducting research related to the geography of Guatemala since 1991. "One of the fascinating aspects of archaeology is that in reconstructing entire civilizations, one can't understand how an ancient civilization worked from just one perspective, so it naturally lends itself to interdisciplinary work," he says.
Additional authors and researchers on Dunning's presentation are Robert Griffin, Penn State University, John G. Jones, Washington State University, Christopher Carr, a UC doctoral student in the geography program and Kevin Magee, who recently completed his PhD in the UC geography program.

iPad Helps Archaeologists

ScienceDaily (Apr. 8, 2011) — New technology is revolutionizing the precise recording of history at an ancient, lost city, bucking a tradition that has been in place for centuries. University of Cincinnati researchers will present "The Paperless Project: The Use of iPads in the Excavations at Pompeii"* at the 39th annual international conference of Computer Applications and Quantitative Methods in Archaeology (CAA). The conference takes place April 12-16 in Beijing, China.

---

UC teams of archaeologists have spent more than a decade at the site of the Roman city that was buried under a volcano in 79 AD. The project is producing a complete archaeological analysis of homes, shops and businesses at a forgotten area inside one of the busiest gates of Pompeii, the Porta Stabia.
Through years of painstaking recording of their excavations, the researchers are exploring the social and cultural scene of a lost city and how the middle class neighborhood influenced Pompeian and Roman culture.
The standard archaeological approach to recording this history -- a 300-year tradition -- involves taking precise measurements, drawings and notes, all recorded on paper with pencil. But last summer, the researchers found that the handheld computers and their ability to digitally record and immediately communicate information held many advantages over a centuries-honed tradition of archaeological recording.
"There's a common, archival nature to what we're doing. There's a precious timelessness, a priceless sort of quality to the data that we're gathering, so we have made an industry of being very, very careful about how we record things," explains Ellis. "Once we've excavated through it, it's gone, so ever since our undergraduate years, we've become very, very good and consistent at recording. We're excited about discovering there's another way," Ellis says.
"Because the trench supervisor is so busy, it can take days to share handwritten notes between trenches," explains Wallrodt. "Now, we can give them an (electronic) notebook every day if they want it."
Wallrodt says one of the biggest concerns of adopting the new technology was switching from drawing on a large sheet of paper to sticking one's finger on the iPad's glass. "With the iPad, there's also a lot less to carry. There's no big board for drawing, no ruler and no calculator."
The researchers say they plan to pack even more iPads on their trip to Pompeii this June. The research project is funded by the Louise Taft Semple Fund through the UC Department of Classics.
*The iPad research experiment, led by Steven Ellis, UC assistant professor of classics, and John Wallrodt, a senior research associate for the Department of Classics, has been featured on the National Geographic Channel as well as Apple's website. That's after the researchers took six iPads to UC's excavation site at Pompeii last summer. The iPads themselves were just being introduced at the time.

Origins Of Maya Blue In Mexico

ScienceDaily (Apr. 23, 2009) — The ancient Maya civilisation used a rare type of clay called "palygorskite" to produce Maya blue. Combining structural, morphological and geochemical methods, Spanish researchers have defined the features of palygorskite clay on the Yucatan Peninsula in Mexico. These findings will make it possible to ascertain the origin of the materials used to produce this pigment, which survives both time and chemical and environmental elements.

---

A Spanish research team has traced the route followed by the Maya to obtain palygorskite clay, one of the basic ingredients of Maya Blue. "Our main objective was to determine whether the Maya obtained this clay from one place in particular," co-author of the study Manuel Sánchez del Río, a physicist at the European Synchrotron Radiation Facility in Grenoble (France), told SINC.
The team, including Mercedes Suárez, from the Geology Department of the University of Salamanca and Emilia García Romero, from the Universidad Complutense in Madrid, analysed various samples of palygorskite clay on the Yucatan Peninsula to compare them to samples from other places. The results are available in the latest edition of Archaeometry.
Palygorskite clay has been used in Mesoamerica since ancient times. Numerous data suggest the Maya were aware of its properties and, what is more, this clay was closely related to socio-cultural aspects of the Mayan culture.
"Present day native communities on the Yucatan Peninsula are familiar with and use palygorskite clay for a variety of purposes, ranging from making candles on All Saints' Day and household and artistic pottery to remedies for mumps, stomach and pregnancy pains and dysentery," Sánchez del Río explained to SINC. Nowadays, modern pharmacology uses clays like palygorskite to produce anti-diarrhoea medicine, a remedy the Maya began to use more than a thousand years ago.
However, palygorskite was mostly used to make the Maya blue pigment, which is produced by mixing indigo, an organic dye obtained from the plant of the same name, with a base of palygorskite clay. The resulting compound is extraordinarily resistant to chemical and environmental elements.
Archaeological sites
The researchers found samples of high-purity palygorskite clay in several locations on the Yucatan Peninsula, in a 40 km radius of the well-known Maya archaeological site of Uxmal. Some of these locations are well documented, but others have been discovered for the first time during this expedition.
The fact that this clay was abundant among the samples collected confirms that the mineral is common on the peninsula.
Crystal-chemical analysis then enabled researchers to obtain the formula for the composition of Mayan palygorskite clay: (Si7.96Al0.07)O20 (Al1.59Fe3+0.20Mg2.25) (OH)2 (OH2)4Ca0.02Na0.02K0.04 4(H20).
These results will be useful for studying archaeological remains with Maya blue and to determine whether the palygorskite clay used in the pigment was taken from Uxmal or the surrounding area.
Maya Blue was invented between the 6th and the 8th Century and can be found in sculptures, fresco paintings, codices and pre-Columbian decorations across Mesoamerica, from the Gulf of Mexico to the Pacific Ocean. It was used during the colonial period to paint frescos in churches and convents. Maya blue was rediscovered in 1931 and scientists were baffled by the stability and persistence of this colour found on objects dating back to pre-Columbian times.
This thousand-year-old pigment, which has proven immune to the passage of time, erosion, biodegradation and modern solvents, is considered the forerunner of modern hybrid materials, compounds of organic and inorganic design with interesting properties for use in high technology.

Electricity from Fuel Cells

Upscale green: A luxury residential building on New York City’s Roosevelt Island receives a fuel cell from UTC Power. Fuel cells are expensive, but they are starting to make economic sense for more businesses.
Credit: UTC Power

Business

Electricity from Fuel Cells

For a growing number of businesses, government subsidies and decreasing costs are making the technology cost-effective.

E-mail   

The new World Trade Center towers in New York City will be powered in part by fuel cells. Whole Foods runs some of its supermarkets on fuel cells. Walmart, eBay, Google, Staples, Coca-Cola, and many other major corporations have installed them in the last few years. Many of these companies say that they're not just using fuel cells to reduce energy consumption and pollution, provide reliable backup power, and attract good publicity. They also aim to save money.
If they're successful, and many of the initial results suggest that they could be, it will be because the cost of fuel cells has dropped significantly over the last few years. They last longer than they used to, and at the same time, local and national governments have provided generous subsidies. "There are an increasing number of cases where the pure economics of adoption make sense," says Kerry-Ann Adamson, a research director at Pike Research. But fuel cells remain an expensive way to generate electricity, and they don't yet make economic sense for all businesses.

Using Heat to Cool Buildings

Hot pack: A display at a conference shows a new material (light green) packed into a metal foam. The material is being used to improve a technology that uses heat energy to drive a cooling process.
Credit: Kevin Bullis

Energy

Using Heat to Cool Buildings

Novel materials could make practical air conditioners and refrigerators that use little or no electricity.

It could soon be more practical to cool buildings using solar water heaters and waste heat from generators. That's because of new porous materials developed by researchers from the Pacific Northwest National Laboratory. These materials can improve a process called adsorption chilling, which can be used for refrigeration and air conditioning.
Adsorption chillers are too big and expensive for many applications, such as use in homes. Peter McGrail, who heads the research effort, predicts that the materials could allow adsorption chillers to be 75 percent smaller and half as expensive. This would make them competitive with conventional, compressor-driven chillers.
All refrigerators and air conditioners cool by evaporating a refrigerant, a process that absorbs heat. They differ in how that refrigerant is condensed so that it can be reused for cooling. Unlike the technology inside most air conditioners, which employs electrically driven compressors to mechanically compress the vaporized refrigerant, adsorption chillers use heat to condense the refrigerant. Adsorption chillers are typically far less efficient than chillers that use electrical compressors, and are bulky and expensive. But they have the advantage of being cheap to operate, since they require very little electricity. "If you have waste heat, you can run it for free," McGrail says.
So far these chillers have been limited to applications where there is a lot of waste heat—such as industrial facilities and power plants—or where electricity isn't always available. Cutting their size and cost could make them attractive in more applications, including in homes, where they could be run using hot water from solar heaters, McGrail says.

The key is improving the solid adsorbent material. In an adsorption chiller, evaporated refrigerant is adsorbed—it adheres to a surface of a solid, such as silica gel. The silica gel can hold a large amount of water in a small space—it essentially acts as a sponge for the water vapor. When the gel it heated, it releases the water molecules into a chamber. As the concentration of water vapor in the chamber increases, the pressure rises until the water condenses.
McGrail is replacing silica gel with an engineered material made by creating nanoscopic structures that self-assemble into complex three-dimensional shapes. The material is more porous than silica gel, giving it a larger surface area for water molecules to cling to. As a result, it can trap three to four times more water, by weight, than silica gel, which helps reduce the size of the chiller.The material also binds less strongly to water molecules. That reduces the amount of heat needed to free the water molecules—making the process more efficient—and speeds up the process of adsorbing and desorbing water by 50 to 100 times, which helps make the chiller smaller. The materials also work with refrigerants other than water, which expands the temperature range at which cooling is possible.
Since current adsorption chillers can be two or three times larger than chillers that use electric compressors, "cutting the size of adsorption chillers by 75 percent could make them competitive," says Yunho Hwang, a professor at the Center for Environmental Energy Engineering at the University of Maryland. The chillers could be particularly useful for cooling with hot water from solar water heaters, since adsorption chillers can use the relatively low-temperature such heaters produce, he says.
One challenge for such applications could be synchronizing demand for cooling with the production of heat—in some cases, it may be necessary to include a costly heat-storage system to make it possible to keep the chiller running after the sun goes down.
The PNNL researchers have been awarded $2.54 million from the Advanced Research Projects Agency for Energy to demonstrate the material in a cooling system. Under the grant, they have three years to optimize the material's performance and incorporate it into a small demonstration chiller.

Nanosatellite Will Look for Alien Worlds

Planet hunter: A new nanosatellite, called ExoPlanetSat, will search for Earthlike planets using novel optics, navigation, and control technology. It’s about the size of a loaf of bread.
Credit: Technology Review

Computing

Nanosatellite Will Look for Alien Worlds

Draper Laboratory and MIT have developed a satellite the size of a loaf of bread that will undertake one of the biggest tasks in astronomy: finding Earthlike planets beyond our solar system—or exoplanets—that could support life. It is scheduled to launch in 2012.
The "nanosatellite," called ExoPlanetSat, packs powerful, high-performance optics and new control and stabilization technology in a small package.
While there have been many small satellites, these are typically used to perform simple communication or observation missions. "We are doing something that has not been done before," says Séamus Tuohy, director of space systems at Draper.
ExoPlanetSat will search for planets by measuring the dimming of a star as an orbiting planet passes in front of it, a technique called transit observation. The satellite's light detector has two focal plane arrays—one for star tracking and for the transit observations. Measuring a star's dip in brightness precisely also allows the planet's size to be calculated. And by measuring the amount of time it takes the planet to complete its orbit, researchers can determine the planet's distance from its star.

This technique is well-established, but has only be used by much larger orbiting spacecrafts, including the French-operated satellite CoRot, which made a significant planet discovery last year, and NASA's Kepler satellite, which launched in 2009.  ExoPlanetSat is not meant to replace larger spacecraft, but to be complementary, says Sara Seager, professor of planetary science and physics at MIT, meaning the nanosatellite will focus on individual stars that larger spacecraft have identified as being scientifically interesting. Whereas a spacecraft like Kepler looks at approximately 150,000 stars, a nanosatellite like ExoPlanetSat is designed to track a single star.
To accurately measure a star's brightness, engineers must keep the spacecraft stable—incoming photons must hit the same fraction of a pixel at all times, says Seager, who is also a participating scientist for the Kepler satellite. "Any disturbances that shake the spacecraft will blur the image and make the measurements unusable," she says. "And smaller spacecrafts are easier to push around."
To precisely control and stabilize ExoPlanetSat, Draper and MIT researchers built custom avionics and off-the-shelf reaction wheels, a type of mechanical device used for attitude control, at the base of the spacecraft to maneuver it into position. Battery-powered piezoelectric drives control the motion of the imaging detector, which is uniquely decoupled from the spacecraft, so it operates separately. (The battery will be charged by solar panels.) "The drives move the detector counter to the spacecraft so precisely the human eye cannot see the motion," says Seager. "This is an order of magnitude better than any nanosatellite has demoed before," she says.
The nanosatellite has a volume of three liters; it's 10 centimeters tall, 10 centimeters wide, and 30 centimeters long. "It was an engineering feat getting all the hardware, including the necessary processing power and data storage, into such a small package," says Tuohy.
Each nanosatellite will cost as little as $600,000 once in production—ExoPlanetSat cost approximately $5 million—and their estimated orbital lifetime is one to two years. Eventually, Seager says, the researchers hope to launch a whole fleet of nanosatellites surveying the nearest and brightest stars.

Sensing Brain Pressure without Surgery

Under pressure: Researchers have developed a noninvasive way to assess high levels of pressure in the brain (as seen in this MRI), which often result from brain injury.
Credit: Photo Researchers

Biomedicine

Sensing Brain Pressure without Surgery

A noninvasive technique could monitor concussions, migraines, and other conditions.

One of the most important things to monitor in patients who've sustained a severe blow to the head or a serious hemorrhage is pressure in the brain. This can reveal an increase in the brain's volume, thanks to bleeding, swelling, or other factors, which can compress and damage brain tissue and starve the organ of blood. Increases in pressure have also been implicated in other, less critical neurological problems, such as migraines and repeated concussions. But current methods for monitoring intracranial pressure are highly invasive—a neurosurgeon drills a hole in the skull and inserts a catheter, which carries a risk of infection.
Thomas Heldt, a research scientist at the Research Laboratory of Electronics at MIT, and collaborators Faisal Kashif and George Verghese, also at MIT, hope to change that with a new, noninvasive method for monitoring intracranial pressure. While the technology is still in its early stages of development, initial studies on data from comatose patients show that it is about as accurate as intracranial monitoring with a catheter and more accurate than other, less invasive options, which involve inserting a catheter into the tissue layers between the inner skull and the brain. Heldt presented the research at the Next-Generation Medical Electronic Systems workshop at MIT earlier this month.
"If we had a way of determining pressure in the field, even a simple heuristic, like whether pressure is greater than 20 mmHg (millimeters of mercury—the standard measure at which physicians intervene), it would be hugely helpful," says Rajiv Gupta, director of the Ultra-High-Resolution Volume CT Lab at Massachusetts General Hospital, in Boston. "Triage is based on that." Gupta was not involved in the research.
To assess pressure noninvasively, Heldt's team started by creating a simple circuit model of pressure in the brain using knowledge of brain anatomy and how blood and cerebrospinal fluid flow through the organ. He then developed an algorithm to calculate intracranial pressure for a given level of arterial blood pressure and cerebral blood flow. Arterial blood pressure can be measured either with a catheter inserted into the wrist, or indirectly with a finger cuff, a device similar to an arm blood-pressure cuff but which provides continuous readings of blood pressure. A noninvasive ultrasound technique known as transcranial Doppler can detect velocity of cranial blood flow, which is directly related to the flow itself.

Researchers validated the approach using previously collected data from 45 comatose patients. The estimate matched the gold standard measure with a deviation of about eight to nine mmHg. Other methods for measuring pressure, such as catheters inserted into the space between the skull and brain tissue, vary by 10 mmHg from reading to reading in the same brain.

Heldt says the goal is to achieve accuracy within four to five mmHg, which will enable physicians to distinguish between a safe pressure—a healthy person's intracranial pressure ranges from about seven to 15 mmHg—and one that requires intervention. When pressure rises to between 20 to 25 mmHg, physicians try to bring it down to a safer range, either through steps as simple as making the patient sit up, or as severe as taking away a piece of the skull to relieve pressure.
Researchers are about to begin a new test of the technology with collaborators at Beth Israel Deaconess Medical Center in Boston using data collected in real time from intensive care unit (ICU) patients. They hope that better-quality data will improve the accuracy of the measure. (The previous data set was collected more than a decade ago, with older equipment.) They also hope to show that a noninvasive method of collecting arterial pressure will work as well as intra-arterial monitoring.
While the researchers are initially focused on validating the technology in ICU patients, where they can compare the measure to intracranial catheters, they say the biggest potential for the tool is in examining patients with mild traumatic brain injury, recurrent migraine, and certain vestibular disorders.
The cumulative effect of mild brain injury is of great concern to both athletes and the military, given growing evidence that repetitive damage can have serious long-term effects. "For mild traumatic brain injury, we don't know what intracranial pressure does," says Heldt. Recent research in rats has shown that exposure to a blast, which generates a pressure wave, triggers an increase in intracranial pressure; the bigger the blast, the bigger the increase in pressure. Eventually, the researchers plan to develop miniaturized devices that could be deployed on the battlefield or the sports field.
Heldt adds that his team isn't the first to try to assess intracranial pressure based on arterial and cerebral blood flow. But previous efforts used data mining or machine learning approaches to create the algorithm. Such approaches require a database of previous measures. If a new patient is substantially different from those in the database, the algorithm fails. By incorporating simple physiological knowledge of the brain, his team could create a model that doesn't require any previous knowledge of the patient or anyone else.

Jurassic Docs

Jurassic Docs
Paleontologists Teach Medical Students About Fossil Tumors

June 1, 2006 — Using medical-physics tools such as CT scans, medical students can learn to recognize a tumor even in a 150-million-year-old dinosaur bone. Paleontologists say the role of disease during evolution can shed light on the origins of some common medical problems. The discovery of osteosarcomas in dinosaur bones has strengthened the idea that dinosaurs grew quickly, more like birds or mammals than like reptiles.

---

PITTSBURGH--Think you have nothing in common with a Tyrannosaurus rex or animals from the Jurassic era? Think again. A first-of-its-kind program combines med students, paleontologists, and cutting-edge technology ... And the program's founders say doctors of tomorrow will be better ... if they study dinosaurs to uncover prehistoric medical links between the present and the very distant past.
What do dinosaurs have in common with people today? More than you might think! Fossil technicians process dinosaur bones to find out. With the use of medical physics such as a CT scan of a dinosaur bone, paleontologists find themselves light-years ahead.
It's a non-invasive way to see what earlier researchers have only been able to guess.
Carnegie Museum of Natural History paleontologist Chris Beard says by studying the evolution of prehistoric animals, today's medical students can understand the origins of some common medical problems.
"This is, as far as we know, the oldest evidence of cancer in the fossil record," he tells DBIS of a softball-sized tumor in a 150-million-year-old dinosaur bone.
First-year med student Katherin Peperzak says, "The first thing I thought was, 'Wow! I didn't realize cancer was that old.'"
Paleontologists learned this is a special kind of cancer called osteosarcoma that, in humans, can develop during a teenage growth spurt.
Beard says these are examples that med students are unlikely to forget. "I think that it'll make them better physicians just in the sense of being able to diagnose a potential osteosarcoma at an early stage," he says. "They'll be more ready to look out for it, just knowing and being exposed to this dramatic example in the past." ...Mysteries from the past, unraveled by research and delicate work in the present.
Paleontologists say they've also gained invaluable insight during their partnership with the University of Pittsburgh School of Medicine. For example, the discovery of the osteosarcoma in the dinosaur bone strengthens the idea that dinosaurs grew quickly, more like birds and mammals do instead of how reptiles grow.

BACKGROUND: Working in partnership with the University of Pittsburgh School of Medicine, researchers at the Carnegie Museum of Natural History have discovered a cancerous tumor preserved in the bone of a 150-million-year-old dinosaur.
LOOKING FOR A DINO'S TUMOR: Using state-of-the-art computer tomography (CT) scans, the scientists imaged the spine and pelvis of a Camptosaurus from the Jurassic era (210 million to 140 million years ago.) This preserved the ossified tendons, providing 3D views so that the researchers could conduct additional studies. The museum will also be scanning a fossil of a primitive lizard that lived 300 million years ago. They will be building 3D images from the pictures. They hope that the 3D images will reveal sutures between skull bones, and thus enable them to characterize the dino's genus and species.
LESSONS OF THE PAST: Some of the most common medical ailments have roots that can be traced back millions of years, when our human ancestors evolved from walking on all fours to standing on two legs: back pain, knee problems and hernias, for example. Doctors can gain an edge by studying the past. Understanding the origins of human disease can help identify new ways to prevent and treat them. Partnerships like the one between the University of Pittsburgh and the Carnegie Museum -- the first of its kind -- can help reveal those origins. For instance, using what is known about the fossil record and anatomical changes over time, scientists can piece together information about how genetics has influenced evolution, and vice versa. More and more physicians are beginning to realize that medicine itself is evolutionary.
ABOUT FOSSILS: Fossils are the remains of organisms like plants or animals that have been preserved through time, usually found buried within thick layers of sedimentary rock. Sedimentary rock is formed as new layers are added, one over the other, over time, with fossils from that specific time period forming within each layer. Because they occur in chronological order in rock formations, the fossil record is like Earth's diary. When an organism dies, it gradually breaks down so that soft tissue, muscle and internal organs decompose. However bones and teeth are more likely to be preserved, especially if buried under sediment. As the material decays over time, minerals dissolved in surrounding groundwater can seep in. The object maintains its original shape, but is now composed of hard minerals: a fossil.
The American Association of Physicists in Medicine contributed to the information contained in the TV portion of this report.