Answer to Question 1
There have been at least six episodes of extensive glaciation: the mid-Archean at 2.9 b.y. ago, the Huronian at 2.3 b.y. ago, the Snowball Earth episodes of the Neoproterozoic at 750 m.y. ago and at 600 m.y. ago, the Late Ordovician glaciation about 440 m.y. ago, the Permo-Carboniferous glaciations about 280 m.y. ago, and the Pleistocene glaciation, which has lasted for the past 15-30 m.y.
Answer to Question 2
The trauma and memories of conflict makes it more difficult for individuals and communities to work together, and an outsider will have to negotiate those issues as well as the regular hurdles in finding solutions to help people improve their lives.
Views of Earth’s Surface
Tides on Earth
Nursing history for nose and sinus assessment
Orbital Motion of Earth and Other Planets
Earth 240 Million Years Ago
The evolutionary history of the mitochondrion and the chloroplast