For thousands of years, the resin of fossilized trees known as amber has fascinated jewelers and inspired the scientific imagination. Especially in the past 200 years, paleontologists around the world have looked to it to understand the ancient past by studying the incredible fossils it preserves.
Do you have questions about amber? Don’t worry, the National geographic has all the answers.
Plants secrete many types of viscous liquids, such as latex, gums, and waxes. Certain types of plants, usually woody, produce resins: complex, sticky substances that do not dissolve in water and harden when exposed to air.
The resins serve to coat plant wounds, turning them into something similar to platelets in our bloodstream. When a resin-producing plant is injured or suffers a break in the surface (such as a crack in the bark of a tree), resin oozes from the area. When left in the open and warmed by sunlight, it begins to harden. This process forms a protective coating over the plant’s wound, helping to keep fungi and other pathogens at bay.
As the resin is sticky, some small creatures can get stuck in it when it drips onto tree bark, soil, or even tree roots. Sometimes these tree parts end up in water, perhaps because the tree was growing on the edge of an ocean or lake, or because a flood washed it into a river. Some of these waterborne resin globules end up buried in sediment, such as sand in a floodplain or sediment at the bottom of a lake.
The deeper the resin is buried over several millennia, the more pressure and heat it will experience. Over an extended period, these conditions cause the resin compounds to polymerize or chemically react with each other to form a tangle of molecular bonds. This process gives rise to the hard, glassy material we know as amber, and it can also preserve, with extraordinary fidelity, the shapes of all small creatures trapped in amber.
It’s hard to know exactly. The transformation of resin into amber is ultimately a product of the conditions the resin drop has undergone. In general, amber is usually over 40,000 years old. If it’s younger, it’s more likely to be classified as copal, an old curing resin that still retains some of the properties of the fresh material, such as a tackier surface.
As amber can envelop and protect even invertebrates such as molluscs, it is ideal for preserving the smallest and most skeletal inhabitants of forest ecosystems. For nearly two centuries, paleontologists studying amber have found insects, arachnids, crabs, plants, fungi, nematodes, plants, microorganisms, and even a piece of a larger vertebrate animal. .
But, as you can imagine, the fossils that end up in amber are those of creatures most likely to be buried in the resin of an ancient tree.
There are more than 160 deposits worldwide where copal or amber has been found, and the oldest on Earth (discovered in a coal seam in Illinois) is approximately 320 million years old. However, these amber slabs are on average only half a centimeter wide and contain no fossils.
Of all the amber deposits on Earth, only a few dozen contain a wide variety of fossils. Almost all of these fossil deposits are 125 million years old or younger, with one well-known exception: a 230 million year old amber site in the Italian Alps that preserves a species of fly and two species of mites.
Baltic amber is estimated to be between 34 and 38 million years old, although some deposits formed earlier. It is eroded by sediments off the coast of the Baltic Sea in northern Europe, and the best-studied deposits come from what is now the Kaliningrad region of Russia.
Over 3500 species of fossil arthropods have been found in Baltic amber, including over 650 species of spiders. On rare occasions, amber produces vertebrate fossils, such as a spectacular gecko (a species of gecko), called Yantarogekko balticus, dated to around 54 million years ago. He also produced plant fossils, such as the largest known fossil of a flower preserved in amber.
Dominican amber is generally believed to be between 15 and 20 million years old, although its exact age is debated. Scientists have found over a thousand fossil species in its amber, including over 400 species of insects and 150 species of spiders. Sometimes vertebrate fossils also appear, such as anoles and even a salamander.
Burmese amber is around 99 million years old and comes from mines in Kachin State in northern Myanmar, which have been mined for the jewelry trade for around 2,000 years.
Scientific interest in Burmese amber has grown over the past two decades as paleontologists have discovered an extremely diverse ecosystem: half-buried carnivorous ants, the partial tail of a feathered dinosaur, the shell of a a sea creature known as an ammonite, and even an ancient bird chick.
However, paleontologists also passionately debate the ethics of studying Burmese amber. Kachin amber mines have been at the center of decades of conflict between the Burmese military and local independence groups, and few recent scientific studies of Burmese amber have included Burmese co-authors.
Canadian amber is around 79 million years old and mostly comes from a place called Grassy Lake in the western province of Alberta. Over 130 different fossil species have been found there, many of which are aphids or mites. But some pieces of amber include evergreen branches, mushrooms, pollen, and even bird and dinosaur feathers.
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