How did the meltdown of the ice age promote migration within the continent?

it melted the ice in the valleys, thus promoting movement of early immigrants southward and eastward along the continent.
it promoted the growth of plants, and thus early settlers began moving inward to warmer places in search for better land for cultivation.
it promoted the development of fishing for food, thus settlers followed the coastline toward the south and east of the continent.
it melted the frozen land bridge between present-day siberia and north america thus promoting movement inward in the continent.
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The Texas oil boom, sometimes called the gusher age, was a period of dramatic change and economic growth in the U.S. state of Texas during the early 20th century that began with the discovery of a large petroleum reserve near Beaumont, Texas. The find was unprecedented in its size (worldwide) and ushered in an age of rapid regional development and industrialization that has few parallels in U.S. history. Texas quickly became one of the leading oil-producing states in the U.S., along with Oklahoma and California; soon the nation overtook the Russian Empire as the top producer of petroleum. By 1940 Texas had come to dominate U.S. production. Some historians even define the beginning of the world's Oil Age as the beginning of this era in Texas.[1]

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