The Sierra Club later expanded its mission to promote the use of alternative energy.
encourage people to enjoy nature.
improve air quality across Florida.
set aside land for conservation.

Why is the huronian supergroup rock formation particularly interesting to scientists? because it looks like a cross-section of a giant, stone encyclopedia because it formed during the period when oxygen began to accumulate in the atmosphere because it contains unusually large amounts of oxygen and sulfur because it dramatically altered the planet's development when it first formed