Wordless Wednesday: Shark Tooth Hunting

Kids' Paleontology: Rocks and Time

 Paleontology!  Old stuff! Realllly old stuff!

We're looking at traces of life from the recent (10,00 years ago), to the distant past (a billion years ago).  Yes, there was life for a couple billion years before that, but it was all single celled so... not as interesting?  Harder to show kids at any rate.

But I did create a one billion year time line!


If one side of a sheet of copy paper is 100,000 years, then the top sheet looks like this.

That bit at the bottom is recorder human history (5,000 years), and the line at the edge is all living people (about a hundred years).

That means two sides are 200,000 years, right? Using both sides, a ream of copy paper is 100 million years, and a case of copy paper is 1 billion years!

I was sorely tempted to get 3.5 more cases of paper so I could do the whole history of earth, but I contented myself with marking  where the cases would be.

Conveniently, the whole 4.5 billion year history of earth would be about the height of my ceiling.

But how do we know where things fit on that timeline?

To understand that, we need to know the rock cycle and radiometric dating.

 The rock cycle is easy: gather up all the broken bits of crayon in the house and peel off the paper.  First we talk about what breaks rocks down: people, wind, water, ice, earth movements, and chemical and biological weathering.

Then we put the crayons in a bag and "weather" them by taking turns whacking them with hammers.

When you are left with crumbly bits of sediment, fold them up in foil and have the kids squish them together as hard as they can. If you are doing this with younger kids, use newer crayons since they stick together more easily- you want them to stick, but still crumble if pressed. This is your "sedimentary rock." Note that you can still see the little pieces, and show them the same effect on sandstone.

Next, rewrap them in foil and hit them with a hammer.  You can also (with tongs) pass them through a flame.  These stick together much better, and represent metamorphic rock. Show them that the little pieces have started to change shape, and compare it to marble.  At this point, you might want to check the foil and rewrap it if the foil tore during the hammering phase.

Lastly, hold the foil packets over a low flame (stove top or candle) until they melt to form "igneous rock."  I compared this to pumice but any igneous rock works.

Once they understand how rock is recycled, you can explain why fossils are only formed in the
sedimentary layers.  We looked at a number of different rocks and fossils.

 I happen to have a large piece of mudstone filled with shell casts and molds (on the right in the picture), and it was helpful to show the softness of the rock (you can crumble it, it's really mud on the way to becoming rock), and how perfectly undistorted the fossils were.

But how do we know how old they are?

The layers the fossils are found in (or between) are dated by using radioactive minerals found naturally everywhere.  For fossils, it's mostly radioactive potassium which decays into argon very slowly.  As in, half of it decays (half life) in 1.3 billion years! That's long enough to date anything from before the planet was formed.  As opposed to carbon 14 which has a half life of  5,700 years - good for dating the last 60,000 years, but nothing older because it's all gone!

I gave the kids a quick overview of atomic structure so they could see that when the nucleus gets too big, having all those positive charges pushes it apart, breaking it into smaller atoms of completely different elements.  Magnets are a good way to show this, and it helps to have a periodic chart.

The important thing is that potassium is a solid, and argon is a gas.  Comparing how much you have of each tells you how long that rock has existed. Since they are inside a rock, the argon is trapped until the rock itself is melted down and the gas escapes, resetting the clock.

To show this, I made a giant candy bar! It started out about double this size.  I had the kids count to 3 repeatedly, and each time they got to 3, I snapped off another piece.

After a while, I stopped and asked them how long we had been doing it. No one knew, so we counted up the pieces and multiplied by 3.

That's basically how this form of dating works.  In real life instead of a straight count of argon (which would vary by sample size), it's the ratio of potassium to argon.

Also, geologists can't eat their sample!

Wordless Wednesday: Natural History Museum, First Floor

Wordless Wednesday: Shark Tooth Hunting

Shark Teeth!

We finally made it out shark tooth hunting!  Since it was after Memorial Day, we went to Purse Park which is (Quiz!):
A Free
B Uncrowded
C Jelly fish free
D Farther away
E All of the above.

I knew that the answer was E because I've been there before.  It's pretty far off the beaten track and the beach itself is in a tidal part of the Patapsco river (which is why there are no jelly fish, but lots of sea shells).

If you aren't familiar with the area, we were on the Maryland side (in the shade!) looking across at Mount Vernon, Virginia (home of George Washington).

What I didn't know was that they must use these back roads to train people who paint lines on the road. Or, possibly, they really like beer here.

For the last half hour of the trip we were quite amused at the weird, wandering, never quite parallel lines.
 
What I also did not know was that the fossils here appear to be twice as old as the fossils at our usual spot.  According to the park service, these shark teeth come from the Aquia formation, from about 60 million years ago - you know, right about the time the asteroid hit.

Also, I left my phone in the car (accidentally), so I missed getting pictures of  us actually finding the fossils.  But find them we did! And I was happy to find my phone still in the car!


We were only there for an hour and a half, but this was our largest haul of fossils ever: 241!

We ended up with 123 teeth, 98 ray plates, 5 bone fragments, and 13 turtellias (like long snails).




And, if that wasn't enough to make it a red letter day,  on the way home, Blue Streak hit 100k!

UPDATE: I forgot to mention that the road photos are courtesy of Klenda (I didn't take them while driving!) and that there are some downsides to Purse Park besides the distance.

I would not recommend going there with young kids because the path to the beach, while a lovely hike, ends in a fairly steep... well, somewhere between a slope and a drop.  Older kids love the challenge, but it would be a nightmare with a toddler or baby, especially if you were also trying to carry anything.

Also, the beach disappears completely at high tide, so check the tide charts before you go!

Wordless Wednesday: Purse Park Expedition

Hppy Birthday, Oob!

 Oob is 8!

He had a great birthday.


 Presents from people who love him!

 A Bionicle cake with swirly colors inside! (Thank you, Klenda!)

And pizza for dinner!

With extra olives!!!





 
A trip to the Bay!

And lots of fossil shark teeth!

In fact, counting ray plates and bone fragments, we found 134 fossils!


And we spent a lot of time just playing in the sand and water.  A perfect birthday!

8 Amazing Things About Oob

1. He's a morning person, a genuine, crack of dawn, smiling morning person.
2. He's a ferocious snuggler.
3. He tells really silly jokes.
3. He loves gummy bacon (lox) and capers.
4. He's fast with a scooter.
5. He's a Wolf Scout, but he's about to be a Bear Scout.
5. He creates costumes out of everything!
6. He can figure out complicated math in his head.
7. He loves to say the Rosary.
7. He loves to give people flowers.
8. He's mastered the art of super fast Lego building.  Wait, does that mean he's a Master Builder?!

Natural History

 So,what do you think Choclo and Oob are hiding from?

Could it be....

A giant T-rex?

Really they were cuddling up in the polar mammals section of Mammal Hall at the Natural History Museum, we didn't find the T-rex until much later.

But we sure were thrilled when we found it!

Dinosaur Hall closed last summer and will not reopen for three and a half years (Choclo and Oob will be 13 and 11!).  They are redesigning the space and installing their new T-rex skeleton.

We were definitely feeling the lack of dinosaur.

But they turned one of their temporary exhibit spaces into a small dino exhibit with their old T-rex skeleton (don't tell anyone, it's really only a cast, that's why they were so excited to get the new real skeleton).

Most of our museum time we spent in the Mammal Hall.  The longer I look at some of our large mammals (rhinos, hippos, tapirs), the weirder they really are, and the closer they look to those Ice Age mammal oddities.

Choclo and Oob were enchanted by the pangolins, and then decided they would like to have pet dik diks (deer the size of dogs with improbably tiny feet).