Dear Reader,
Ancient bits of history that map out a vision of our land as never imagined before… fossils fascinate the paleontologist in all of us. Even if Wisconsin cannot boast that it’s home to dinosaur fossils, if you look closely enough, its soils and stones deftly display layers of rocks, minerals, and fossilized life, giving us glimpses into some of history’s mysteries, such as the evidence of a shallow tropical sea once covering our land. It was a sea that teemed with an amazing variety of early life forms: palm-sized trilobites scurrying over colorful starfish; large tentacled cephalopods, ancient ancestors of today’s squids and octopuses, pulsing over coral reefs; and crinoids, marine animals resembling tall alien lilies snatching tiny food particles from the seas with feathered arms.
We have a trilobite fossil in our house — it’s a reminder of past eras and the amazing geologic process of turning life into stone. Learn in this newsletter about the processes rocks go through and how to start your own rock or mineral collection — and maybe you’ll find your own inspiring specimen!
Enjoy!
Brenna & Betsy
The Folks at Nature Net
November
Rocks, Minerals, and Fossils
“All the fossils that we have ever found
have always been found in the appropriate place in the time sequence.
There are no fossils in the wrong place.”
– Richard Dawkins
Did You Know?
Wisconsin’s state fossil is the Trilobite. These ancient arthropods swam the earth’s seas over 520 million years ago (examples are pictured at left), and their fossils are very abundant around our state and region (see below for tips on where to look!). There are over 20,000 species of described trilobites, ranging in size from 1-70cm, and more are being discovered each year. These Paleozoic Era creatures went extinct 250 million years ago. Related to modern lobsters, horseshoe crabs, and spiders, and looking a bit like giant sowbugs or pillbugs (tiny modern land-based crustaceans you can find under any backyard rock), many trilobites possessed a head, thorax, and tail. The name “trilobite” means “three-lobed,” and refers not to these three body parts, but to the three grooved lobes running the length of the body.
Wisconsin also has a state rock: Red Granite. This igneous rock is made up of quartz (the clear crystals), feldspar (which can be many colors but is red or pink in red granite), and mica (the dark, shiny specks). The word “granite” comes from the Latin term for grain — which refers to the granular look of the crystals. Granite’s crystals are visible with the unaided eye because they formed slowly below the earth’s surface (that makes it an intrusive igneous rock).
Wisconsin’s oldest rocks date from the Precambrian eon — that’s over two billion years ago. But if you want to find fossils in Wisconsin, you’ll need to find rocks much younger than that. Rocks from the Paleozoic Era (500-200 million years ago), when warm shallow seas covered the land, often reveal fossil evidence of life from that time. No, not dinosaurs, but plenty of brachiopods, trilobites, corals and more. Find out more from the Paleontology Portal and the Virtual Silurian Reef!
There are over 4,500 known mineral species on Earth. Rocks can be made up of a combination of minerals, like red granite, while others, such as limestone, are composed primarily of just one mineral — in the case of limestone, it’s calcite. Still other rocks are not made of minerals at all. Coal, for example, is a sedimentary rock made of formerly-living carbon from ancient peat bogs. Most gemstones are minerals — in fact, rubies and sapphires are different colors of the mineral species corundum, and emeralds and aquamarine are varieties of the mineral beryl.
What To Do This Month:
Stop in at the UW Geology Museum’s Storytime for pre-schoolers. Offered at 10:30am every 1st and 3rd Thursday of the month, this walk-in event includes a story, a special peek at museum specimens, and a craft to take home. Stop in any day of the week (or Saturday mornings) to check out the glittering mineral collection and the ultraviolet light room where rocks and minerals show their otherwise hidden colors.
Do your own fossil hunting! Check out this past Nature Net News for tips and find advice in this Wisconsin fossil forum. And scope out some good nearby fossil sites here!
Get out the beakers and measuring cups and try a few at-home mineral experiments. With just a few household items, you can replicate the creation of a geode, grow your own crystals, or witness crystallization while you make rock candy.
Take a tour of your own house — you just might find minerals all around you!
Instant Outdoor Expert:
The Rock Cycle
You may be familiar with the water cycle, but did you know there is also a rock cycle? It may seem rocks never change; however, thinking of them in a geologic (rather than human) lifespan, reveals that in reality, rocks are always changing form. There are five basic processes that can transform rocks: heat & pressure, melting, cooling, weathering & erosion, and compacting & cementing. For example, if we follow the life of a mineral, starting as liquid magma inside the earth, it may cool to create an igneous rock. From there, it may metamorphose under heat and pressure into a metamorphic rock, or it may erode into sediment. As sediment, if may undergo compacting and cementing to form a sedimentary rock. From there, the rock may erode back into sediment, or, with heat and pressure, again become a metamorphic rock — which can then melt back into magma… Think you’re ready to take a rock cycle quiz? Brush up first with this rock cycle diagram.
Need primer on the three basic rock types? Try these three sites for information geared to all ages: igneous, metamorphic, and sedimentary.
Related to the rock cycle, fossil formation incorporates the presence of a living thing. Learn more here!
For Families:
Tricks of the Trail – Rock Collecting
Starting a rock collection is as easy as 1, 2,3. Just collect, observe, sort, and display. Simply using texture, shape and color, you and your young geologist can sort rocks and minerals and even speculate what they are made of or where they came from. Rocks can help us figure out how mountains or valleys formed, where glaciers once flowed, or what ancient creatures looked like. If you’re up for a more in-depth investigation of your rocks, you can record information on each find using the following list of characteristics or physical properties: color, luster, specific gravity (how heavy it feels), shape of crystal, cleavage (the pattern in which it breaks), toughness (how easily it falls apart), hardness (what scratches it), and special properties (like magnetism or fluorescence). Once you’re done investigating your rocks, and perhaps identifying them, you can label them and find a unique way to display them.
Need more help identifying your rock or mineral? Take this on-line identification quiz to figure it out.
Featured Nature Net Site:
UW Geology Museum
Established in 1848, the UW-Madison Geology Museum has spent more than 165 years gathering geological curiosities from around the world. Its mineral exhibits are bursting with colorful crystals and include many fine specimens from the lead-zinc mining district of southwestern Wisconsin. Fearsome skeletons of dinosaurs and other creatures from the distant past — including Wisconsin’s Boaz Mastodon — dominate the fossil display area. Visitors can also view gemstones, petrified wood, mammoth fur, and rocks that glow under ultraviolet light. In addition to an exhibit of meteorites that landed in Wisconsin, the museum also has the only piece of a meteorite from Mars on display in our state
The Museum is open free of charge Monday thru Friday from 8:30am to 4:30pm and on Saturdays from 9am to 1pm. You can take a self-guided tour with a booklet filled with fun facts and tips on what to look for.
See if you can find the stromatolites — the fossilized remains of Earth’s main source of ancient atmospheric oxygen — or fossilized jellyfish captured in a slab of Wisconsin rock. What does that tell you about Wisconsin’s past?
Nature Craft:
Salt Dough Fossil
Start by creating a home-made salt dough:
Mix four cups of flour with one cup of salt and add one to two cups of water to achieve a desired consistency of dough.
Roll the dough out to about an inch thick and cut into shapes, using an inverted cup or soup can as a cutting tool if needed.
Next, using real or plastic leaves, dinosaur figurines, or other natural and household items, press items into the dough to leave textured impressions on the surface. Be creative!
Now, wrap a baking sheet in foil before setting your fossils on top.
Bake for 2 hours at 350 degrees.
To create the ancient, weathered look:
Once your fossils are cooled, paint them with water-based earth-toned paints. Use a cloth napkin or towel to wipe away excess paint as you go. Keep adding layers of paint and wiping some away to add texture and patina. After the paint is dry, you can coat your fossil with a lacquer to add luster and help preserve your finished product.
Suggested Reading:
“Digging Up Dinosaurs (Let’s Read and Found Out)” by Aliki (4-8 years)
“Buried Sunlight: How Fossil Fuels Have Changed the Earth” by Molly Bang & Penny Chisholm (4-8 years)
“Let’s Go Rock Collecting” by Roma Gans (4-8 years)
“Everyone Needs a Rock” by Byrd Baylor (4-8 years)
“The Best Book of Fossils, Rocks & Minerals” by Chris Pellant (5-8 years)
“National Geographic Readers: Rocks and Minerals” by Kathleen Weidner Zoehfeld (5-8 years)
“Geology: A Folding Pocket Guide to Familiar Rocks, Minerals, Gemstones &Fossils” (7+ years)
“Fossils (A Golden Guide from St. Martin’s Press” by Frank Rhodes (7-12 years)
“Geology Rocks! 50 Hands-On Activities to Explore the Earth” by Cindy Blobaum (7+ years)
“Rocks, Fossils, and Arrowheads: Take Along Guides” by Laura Evert (9-12 years)