QUESTION TYPE: Most Strongly Supported
FACTS: Nahcolite formed in salty lates during the Eocene. Labs tests show that nahcolite can only form in salt water where there is 1,125 PPM CO2.
ANALYSIS: Since lab results show that nahcolite formed in salt water during the Eocene, it’s probable that there was 1,125 PPM CO2 during the Eocene.
This is a ‘most strongly supported’ and not a ‘must be true’ because it’s possible the lab results are wrong.
- We have no reason to think that CO2 was lower for most of the 50 million years since the Eocene.
- We have no reason to believe CO2 levels changed during the Eocene.
- We have no information about lakes in general. We just know that some salty lakes had nahcolite.
- CORRECT. This is probably true, because nahcolite needs 1,125 PPM to form in salty lakes.
- We don’t know much about nahcolite. Maybe it forms easily in non-salty lakes, no matter what CO2 levels are. We have no reason to believe Nahcolite only formed in the Eocene.