Blog

What is responsible for the ridge at AL 3?

Check the box next to “Mona Formation, Michigan”. Double click to fly there. Click on the placemark to view the sample taken from this location. This Archean metamorphosed basalt (aka “greenstone”), dated~4.0 Ga, was collected from an outcrop revealing another area of the Canadian shield in Michigan.Based on what you know about basaltic igneous environments, proto continent formation, and types of metamorphism, order the likely events of this time in Earth’s history.Tip: Review figure 11.2 in your book

What is a likely explanation for the changes we see in the fossil record (like at House Range) at this time?

Precambrian Era

You calculated the age of the oldest preserved Earth material above, however, we know from dating meteorites that the Earth is 4.54 Ga. What was happening in that block of time to prevent material from being preserved?

Select the Global Paleogeographic Model folder. Double click to zoom out. Also select the placemark labeled “Question 39” and navigate to where it is in view. It represents the average location of North America during this time. Toggle through the end of the Triassic (~200 Mya) through the Jurassic (~140 Mya).What changes do we see? Mark all that apply.

Turn on the photos database in the Layers panel. Fly to each of the locations in the Question 13 folder. Each outcrop seen is dated 2.4-1.8 Ga. Explore the images in the area by selecting the icons indicated in the descriptions below each location in the folder (If you don’t see them immediately, try zooming in/out). What do they all have in common?

Zircons contain a radioactive isotope called Uranium-238 which has a half life of 4.5 billion years (Ga). How old are these minerals?Tip: 4.5 Ga*how many half lives(don’t round up/down)=age

Open the “Angel Lake, Nevada” folder. Check the “Angel Lake, NV” placemark to fly there. What carved this valley?Tip: Consider its shape

Turn on the “Deserts Overlay”. What kind of desert produced this dune field?Tip: Use the overlay to determine which desert it is part of then decide what kind of desert it is.