Amber: Using "Tree Tears Turned to Stone" to Teach Biology, Ecology, and More! in Greek Mythology, Phaeton's Sisters Are Transformed into Trees after Their Brother Perishes While Driving the Chariot of His Father, the Sun. as the Sisters Continue to Mourn, Their Tears, Exuded as Resin, Are Eventually Transformed into Stones of Amber by the Sunlight

Article excerpt

What if we could take our students on a time-travel field excursion to study animals and plants that lived tens of millions --and even hundreds of millions-of years ago? Would our students enjoy investigating whether modern science can recreate some of these extinct life-forms, including the wooly mammoths and dinosaurs? What about tracing the science--as well as the history--behind prized gemstones? Would students relish a journey from these prized jewels of the Stone Age, through the adornment of kings, to the construction of an entire palace room made with these gems?

If even one of these topics piques student interest, then amber offers an intriguing vehicle to probe biology, ecology, geology, and chemistry concepts, and conveniently bring interdisciplinary science research into the classroom. Amber is a fossil by itself, and can also contain plants and animals that lived millions of years ago. Some of these perfectly preserved specimens give scientists a convenient window to past environments, including the biology, ecology, geology, and chemistry of Earth's past. Through amber, students can study botany (tree anatomy and properties of resin), entomology (morphology and representation of insects trapped in amber), evolution (extinct, trapped insects and resin-producing trees), ecology (environments in which trees grow, and in which amber is preserved), chemistry (desiccation, preservation, and polymerization), and geology (properties of minerals, fossilization, ancient Earth environments, and plate reconstructions from past geologic periods).

Teacher background material: The composition of amber

Amber is fossilized tree resin. Sometimes confused with sap, resin is quite different. Whereas sap carries nutrients and food to the plant, resin serves as a defense mechanism. Some tree resins have antimicrobial and antifungal properties, and can act as a deterrent to several different types of insects.

Not all resins are alike, but instead parallel the differences in the individual trees that secrete them. Frankincense, the often-mentioned historical incense, comes from the resin of Boswellia trees (Figure 1). Initially a sticky mass, resin slowly hardens as polymerization reactions occur. Eventually, the resin reaches the copal stage, and is no longer sticky. After millions of years, the hardened copal attains the fossil stage, and finally is classified as amber. There is no concensus about the compositional parameters of "copal" and "amber." However, the fossilization process, like most fossilization processes, takes millions of years. The oldest amber dates to the origin of resinous trees, or the Carboniferous period of the Paleozoic era, more than 300 million years ago. At this time, huge amphibians roamed the Earth's swamps.

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Because amber starts from an organic source and is not a crystalline substance, it is not classified as a mineral, although the term "gemstone" is still used to describe it because of amber's rarity and aesthetic value. Amber is most often classified as a mineraloid, an amorphous solid. It is not very hard (approximately 2-3 on the Mohs scale), and it can fracture fairly easily. When it is exposed to light and air, amber often develops surface cracks (Figure 2). The benefit to amber's softness is that it can be readily carved. However, it is not nearly as permanent as quartz or similar minerals.

CSI Amber: The crime scene

Once resin reaches the amber stage, this mineraloid can be considered a fossil by itself since it consists of the fossilized remains of tree resin. However, when amber's sticky origins are considered, it seems logical that different leaves, insects, and even small reptiles could be trapped in the original sticky goop. Remains preserved in amber are "evidence" from the original geologic "crime scene."

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Resin can be exceptionally sticky, and organisms caught against the resin only serve to deepen the resin's hold with their struggles. …