But for short-sighted geologist, the earth IS a closed system.
What "short-sighted" geologist are you referring to?
I don't know of any geologist who claims the "earth is a closed system."
Should know, known plenty in my time (BS, Geological Engineering, 82, New Mexico Institute of Mining and Technology).
Obviously the Earth is not a "closed" system. In addition to the solar power of the sun as Coragyps pointed out, you have nuclear decay, hence nuclear power, and, because of gravity itself, you have geothermal power.
I don't know what you are referring to when you say "short-sighted geologist" but is obviously does not refer to anyone with a bachelor's in any earth-related science at NMT as Physics 121 is a requirement for graduation.
Experiences at other colleges may vary, perhaps you are referring to graduates of Liberty "university."
The problem with knowing everything is learning nothing.
If you don't know what you're doing, find someone who does, and do what they do.