Proterozoic II, Cambrian, & Ordovician

Why did “Snowball Earth” happen?

land was at the equator and the temperatures were cold

Explain the process of Snowball Earth

land convened at the equator

temperatures were low

cold water at the poles was easy to freeze

tropical ocean is hard to freeze, but with newfound land it became easier to freeze

What does CO2 and weathering have to do with Snowball Earth?

increased weathering decreased atmospheric CO2 concentrations

weathering on land + water causes stronger weather

it was rainiest at the tropics, which at the time had the most land

therefore as weathering increased, temperature decreased which led to Snowball Earth

What is bilateral symmetry?

nerves developed at the front first (followed by the brain, nose, eyes, etc.) and this was because we generally move forward so we want to know what is in front of us

What does the expansion of eukaryotes correspond with?

rise of atmospheric O2

In what age were the trilobites most abundant and how many variations were there?

late Cambrian with 63 different variations

What was the geological range of the trilobites?

Cambrian-Permian

What was the worst extinction event for the trilobites (as in which event led to the biggest drop in population, not complete extinction).

Ordovician extinction

When did the trilobites fully go extinct?

Permian

What’s one sediment process that we attribute to trilobites and why?

bioturbation because we see calm sediment early Cambrian before the trilobites and then chaotic sediment over the Ordovician

What is the Taconic Orogeny?

the taconic island arc in the iapetus ocean subducted under proto north america, effectively clsoing the western iapetus ocean. the collision of the taconic island arc with proto north america effectively created the taconian orogeny