Friday and Monday April 3rd and 6th (4 Total Tasks)
So the purpose of the first activity for this unit was to show you that lots of things are different on Earth than on the Moon. Key takeaway, most small meteors burn up in Earth's atmosphere, which the Moon does not have. Most craters that do form on Earth are erased by Weathering and Erosion.
As I introduce every unit, I will summarize what we have learned so far this year! We have learned about the shape and size of the Earth, how to map Earth's surface, and how to pinpoint locations on Earth's surface. We have learned the materials that make up Earth and how we humans use those materials. We have learned about the internal structure of the Earth and how it allows for and causes the motion of tectonic plates, which in turn cause volcanic eruptions, earthquakes, and tsunamis. Just recently we learned about Earth's history, how we generally determine the order events happened, and how to determine the real ages of things like rock layers and dinosaur bones.
This unit will now show you that once rock and mineral is formed at Earth's surface, there are processes that occur on Earth to change the rock, break up the rock, and move the rock material. This is the unit of Weathering and Erosion, the breakup and movement of material at Earth's surface. Rainfall, changing temperatures, moving glaciers, waves pounding shorelines around the world, tree roots penetrating rock and soil on most land on Earth, and winds blowing around sand in deserts all contribute to the breaking up, constant smoothing out and erasing of Earth's surface. Mountain ranges are literally broken apart, washed out to oceans and then deposited onto the bottom of the oceans. Earth's surface is just temporary. Over geologically long periods of time (millions to billions of years), Earth's surface is worn down and rebuilt again, over and over. This unit focuses on the processes that change the surface of Planet Earth.
Here it is important to note, that NONE of these processes happen on the Moon!!! The craters you saw in the introduction activity (and that you can see when you go out tonight and look at our beautiful first quarter Moon!!) have been on the Moon's surface for not just millions of years, but likely billions of years. If a meteor like the one that flew towards Russia back in 2013 that you watched video of, crashed into the Moon, it would have struck it at 40,000 mi/hr and created a large, quarter mile to half mile size crater that would then stay visible on the Moon's surface for the next billion or 2 billion years or more!! On Earth however, we too have had thousands and hundreds of thousands, and maybe even millions of impact craters. However, because of rain, moving glaciers, wave action, temperature changes, tree roots growing into rock, sand blowing around, and rivers flowing over all land surfaces, those craters are quickly (geologically speaking) filled in, washed away, and destroyed. In fact only recent craters or very large craters are still visible on Earth's surface. The one in the photo, Barringer Crater from your first activity by the way is a little over 1 kilometer (.8 miles) wide and is located in Arizona and is estimated to be about 50,000 years old. Think about why it still looks so fresh? What do you think it would look like if it was located in New York State? What if it had hit Greenland or Antarctica? Would we still be able to see it?
So our introduction activity was really to show you that there are a couple of reasons that Earth is not pockmarked with craters like the Moon clearly is. First of all, many of you noted that, like the meteor in Russia from 2013, most meteors that are about the size of a semi-truck (tractor trailer) or smaller burn up in our thick atmosphere of Nitrogen and Oxygen. We do ocassionaly get struck by larger meteors like the one that formed Barringer Crater in Arizona (diameter of object was about 160 feet we think, which is about twice the size of the infield of a baseball diamond moving at thirty to forty thousand miles per hour!!! But second of all weathering and erosion usually erase even those craters within a hundred thousand years or so unless they are really big. As noted in the assignment, we do think Earth and the Moon have likely been struck a similar number of times, so without weathering and erosion, North America on Google Earth would be covered in hundreds of tiny, medium, and large craters all over the place just like the Moon! That certainly is not the case!! Now go learn why not!
Here is a quick outline of the weathering processes of this unit. Hopefully this will help you see the big picture, and not get to stuck in the details of each.
Earths rocks and minerals are broken up by the process we call Weathering.
There are two types of weathering, Mechanical (also called Physical) and Chemical Weathering.
Mechanical is the physical breakup (think of it as natures jackhammer or sledgehammer) is by Exfoliation(Thermal Expansion), Frost Action (Ice Wedging), Root Action, and Abrasion.
Chemical Weathering is by water or acids softening up or dissolving rock.
They combine to turn solid rock mountain chains and bedrock into sediment, soils, and dissolved minerals.
VIEW - Photos below that I would normally show in class to help you picture these processes.
3. Root Action - Very start of rock breakup after solid rock forms from a Hawaii Lava Flow. It will likely take 50 to 100 years for this area to become covered in vegetation, and 500-1000 years for soil to begin to form.
4. Abrasion in Deserts - Pedestals form as wind blows sand around only near the ground, wears away the bottom of rock faster. Eventually tips over and process continues until the big boulder is all sand particles too!!!
TAKE NOTES - Complete the noteset (Pgs 1-2) posted in MS Teams (Physical Weathering Noteset) by the end of the day Monday, April 6th. You can either digitally complete, or print out and handwrite them.
READ - Review Book section on Physical (Mechanical) Weathering and complete questions on Physical Weathering.
Monday-Tuesday March 30/31
READ- The article on MS Teams titled - Asteroid the Size of a City Block....note the publish date of May 2018. So this was recent, but did not just happen this week.
WATCH - The YouTube video link here showing a variety of live video clips of a February 2013 Bollide (Meteor) Impact in Russia. Think events like these only happened in the past??? Think Again!!! Yet another reason I love Earth Science. How crazy and neat is this?? Just watch.
COMPLETE AND SUBMIT- In MS Teams I have posted an activity that you need to complete either alone or with a friend if you want to discuss together on Facetime or any other platform. If you complete together, just list the names of both people at the top but still submit copies for each person in MS Teams for grading purposes. Both group members will receive the same grade. This activity is intended to really get you thinking about several of our units in this course. It ties together Astronomy, Earth Surface Processes(this unit we are starting!), Meteorology (Atmospheric Science), and even Rocks and Minerals. Now get brainstorming!!
All 4 activities need to be complete by Tuesday, March 31st at 9pm. We will discuss the importance of all this in a lesson on Wednesday!