How have technological advances in transportation made migration easier, from the age of exploration to modern times?

I would recommend using this concept:

Think about the ways you get from place to place now. You can use a vehicle, a bike, a train, and a plane. The Age of Exploration was the beginning of many of these advances.

81 is a composite number

Humid continental climate is found in the interior of continents between the 30 and 60 degrees latitude, but usually above the 40 degree line.   40 degrees north of the equator means less direct sunlight and therefore less warmth.   this climate is mainly found in the northern hemisphere since there are no major landmasses in the southern hemisphere.  if you live in northern indiana, you know all about humid continental because that is the climate type you have!