Author Question: When did the ozone layer become thick enough to provide an effective UV screen? What will be an ... (Read 41 times)

SO00 · **on:** Jul 14, 2018

When did the ozone layer become thick enough to provide an effective UV screen?

What will be an ideal response?

Question 2

During the Soviet era, every Central Asian republic capital had a(n) ________.

A) Orthodox Christian cathedral
B) mosque converted to city hall
C) opera and ballet theater
D) statue of Lenin posing with a local legendary hero

k2629 · **Reply #1 on:** Jul 14, 2018

Answer to Question 1

The O3 layer should have been absorbing most UV radiation by 2.3 Ga, as soon as O2 levels began to rise. An O2 level of 1 PAL is sufficient to create an efficient ozone screen.

Answer to Question 2

C