The visitor is greeted by great logs that look like they have been carved from stone.
The different pieces come in a rainbow of colors.
You soon learn that petrified wood forms under special circumstances that allows minerals to seep into the cells of the wood and harden. Iron oxide makes the petrified wood look red or orange (rusty), whereas manganese oxide produces blues, purples or black. Other compounds may cause the petrified wood to be greenish or yellow.
Activities:
If you have a piece of petrified wood (often available at rock shops), look at it with a hand lens. See if you can identify the tree rings, or other structures that were parts of the original tree. A few of the logs we saw had remnants of bark.
Sometimes you can identify the type of tree the wood came from. For example, the Texas State Stone is petrified palmwood, coming from a petrified palm tree. (Technically a fossil, petrified wood is also Arizona’s state fossil.)
This week we have a few wonderful resources for learning more about dragonflies and damselflies.
Introduction to Dragonflies and Damselflies
What is a dragonfly and what is a damselfly?
Dragonflies are the large, showy insects that you see around ponds and other bodies of water. When they land on a plant or other object, they hold their wings straight out.
Damselflies, on the other hand, are usually a bit finer, more delicate looking. They rest with their wings folded behind their backs.
Look closely and you will see they often sport bright colors, such as red, green and bright blue. They can be just as colorful and fun to watch as birds or butterflies.
Dragonfly and Damselfly Life Cycles
The adult female dragonflies and damselflies lay their eggs in the water, or on plants or debris in or near the water. The eggs hatch into nymphs (sometimes also called naiads) that feed on other organisms in the water. After a year or two, they crawl to the surface and the adult emerges. There is no transitional or pupal stage.
1. Dragonfly watching
Nothing beats strolling out to a pond, stream or lake and simply watching dragonflies and damselflies in action.
One of the first things you notice when you see dragonflies or damselflies is their strong ability to fly. They have four wings, and can move the fore and hind wings independently. Their wing movement may not be easy to see until you capture them on film.
In this video clip, you can see a dragonfly’s amazing flight slowed down.
Often dragonflies are searching for food when they are flying. They catch other flying insects, such as mosquitoes, while on the wing. In this video you can see dragonflies catching flying termites (although the video title identifies the prey as ants).
According to a recent newspaper article, Arizona dragonfly watching a growing hobby at the Arizona Republic, dragonfly watching is increasing in popularity. Several of our local nature areas are now offering dragonfly walks lead by experts. Check in your area for local events related to dragonflies, especially in the summer.
2. Dragonfly Swarms
I recently found a wonderful blog called The Dragonfly Woman. University of Arizona Entomology Ph.D. student Christine Goforth has started a citizen science project about dragonfly swarming (more about that in a minute), plus has loads of cool information about dragonflies and insects in general.
What is a dragonfly swarm? When a group of insects gather together in a large group, for whatever purpose, it is often called a swarm. In the case of dragonflies, the swarm may be a bunch of dragonflies feeding together at one location. This is called a static swarm. Dragonflies can also form large groups and move from place to place. This is called a migratory swarm.
You might like to see Dragonfly Woman’s posts about making a dragonfly collection using a scanner as well. I love the idea of being able to preserve the insect’s image and let the dragonfly go again.
You won’t believe how many science projects you “can” do with a couple of tin cans.
With a tin can, you may investigate sound vibrations, friction, kinetic energy, potential energy and many more aspects of physics.
Before we start the physics, however, let’s do a bit of chemistry. Is what we call a “tin can” really made of tin? How would you check?
It seems that the can our beans come in should be called a steel can because it is made mostly of steel, although it may have a light coating of tin to prevent rusting. Technically, if a can were made only of tin a magnet should not stick to it. Magnets are attracted to cans that contain iron, usually in the form of steel. Is a magnet attracted to your can of beans? What about an aluminum soda can? Pick up a magnet and find out.
What got us started with tin cans this week was an article in a book that promised you could get a tin can to roll uphill. When it did not work as the book suggested it should, we decided to investigate further.
Activity 1. Uphill Rolling Can
Gather:
Clean, empty tin can* or similarly-shaped plastic container
modeling clay
cookie sheet or similar flat surface and a couple of books to make an adjustable ramp
rubber bands (optional) to give the can more grip
* Remove the lid of the can with adult supervision, and make sure there are no sharp edges.
Roll the can across the floor or on a table to see how it behaves. Build a ramp with a slight incline with the books. Try to roll the empty can up the ramp. What happens?
Now roll out a lump of the clay into a worm or snake shape. Attach the clay to one side of the can on the inside (see photograph). Roll the can across the floor or table. Does it behave differently than it did without the clay?
Try the ramp. Start the can with the clay up versus the clay down, until you can get the can to roll uphill. If it doesn’t work for you, adjust the steepness of the ramp. You can also put rubber bands around the outside of the can to increase grip. Make sure they are even so they don’t over balance the can.
Activity 2. Tin Can Car
You can take the idea of a self-propelled tin can a step further by creating a rubber band-driven version.
The idea is to put two holes in each end of the can (or can lids) that line up with each other, slip a rubber band (or similar elastic material) through the top holes and then add a weight in the center, in the middle of the can. Slip rubber bands through the bottom holes. Tie the ends. Roll the can and it should roll back on its own from the weight in the center.
Description of a similar device from the November 1910 issue of Popular Mechanics. Be aware that ideas of safety were different back then. For example if you try this one, you should use a zinc sinker (available at fishing supply stores) rather than lead.
Activity 3. Tin Can Telephone
A classic activity is to make a telephone using two tin cans and a piece of string.
Gather:
two clean, empty cans with the tops removed (or plastic cups work, too)
nail
hammer
goggles (for eye protection while hammering nail into can)*
string at least a few feet long
*Unlike in the video below, children should perhaps wear eye protection while creating the hole in the bottom of the can.
Hammer the nail into the center of the bottom of each can to create a hole. Remove the nail. Feed the string through the holes and tie a knot so that the knot prevents the string from coming out through the bottom. Both cans should now be connected by the string. Hold the two cans far enough apart so the string is tight. Take turns talking into the can and then listening to the other person talk.
You can even decorate your can like they did in this short video.
Activity 4. Musical instruments
1. Drum
Gather:
clean, empty can or cans of various sizes with the tops removed
large balloons, at least one per can
scissors
chopsticks (optional)
Cut the stem off of a balloon and roll it over the top of a can. This is not as easy as it sounds, but if you can get a tight fit you will have a wonderful drum. Use hands or chopsticks to drum on the balloon top. Compare sounds of different-sized cans.
bin large enough to accommodate the two cans standing up plus sand
Fill a large bin with play sand. Press one can into the sand with the open end down. Press the other into the sand closed end down. Which has the most resistance? Sounds simple, but there are some complex physics involved.
