Act 1
1. How long will it take for the lava to cover the field?
2. Write down a guess.
First, this task is a complete copy of Dan Meyer’s volcano lesson (this whole blog is inspired by him, so no surprise here!). However, I decided to make this despite the similarity because it sets up perfectly for what we’re learning in class next week (sector areas).
Second, this image is from Daily Overview. Here’s the description from the site:
Pivot irrigation fields surround a lava field known as The Cinders, in Millard County, Utah. Along with farming, one of the elements of Millard County’s economy is fossil digging as Trilobite fossils are relatively common in the region west of Delta.
Act 2
3. What information would be useful to figure this out?
4. Write down some questions you have in your head right now.
Act 3
HSG.C.B.5
Derive using similarity the fact that the length of the arc intercepted by an angle is proportional to the radius, and define the radian measure of the angle as the constant of proportionality; derive the formula for the area of a sector.
G.12(C)
apply the proportional relationship between the measure of the area of a sector of a circle and the area of the circle to solve problems
Daily Overview / Satellite imagery courtesy of Digital Globe / Benjamin Grant
When Math Happens 
Thanks this is very good! I will be using this next week with my class. It will be fun.
Just a general comment about 3 Act Math: I think these lessons could be improved slightly by providing a sample solution as an attachment. It just saves the instructor a little bit of time when creating the lessons.
Thank you for the feedback, Patrick! I appreciate it. A sample solution is a great idea! Hopefully I can start adding those in at some point.
Also it looks like the jpeg in act 2 under the downloadable materials has a different value than what’s posted here
Thanks for catching this. I made a mistake in the first draft of the task and forgot to change the downloadable materials. Should be fixed now!