(n) an advanced stage of human society, in which a high level of culture, science, industry, and government has been reached.
Civilization
(n) someone who studies the buildings, graves, tools, and other objects of people who lived in the past.
Archaeologist
(n) a large group of people who live together, sharing the same language, culture, and history, especially those who do not live in towns or cities.
Tribe
(n) an army or country that uses force to enter and take control of another country.
Invader
(n) the beliefs and worship of a god or gods.
Religion
(n) something valuable (such as money, jewelry, gold, or silver) that is hidden or kept in a safe place.
Treasure
(n) a large amount of water covering an area that is usually dry.
Flood
(v) to find something for the first time, or something that had not been known before.
Discover
(n) a situation in which there is not enough of something.
Lack
(n) the broken parts that are left of an ancient building or town.
Ruin
(n) a long period where there is little or no rain, leading to a shortage of water.
Drought
(adj) of or from a long time ago, having lasted for a very long time.
Ancient
(n) a severe tropical storm with high winds and heavy rain.
Hurricane
(n) a severe snowstorm with strong winds.
Blizzard
(n) an extremely large wave, usually caused by undersea earthquake, volcanic eruption, or coastal landslide.
Tsunami
(n) a large amount of ice, snow, and rock falling down the mountainside.
Avalanche
(v) to form or have a mental picture or idea of something.
Imagine
(v) to fall down suddenly because of pressure or having no strength or support.
Collapse
(v) to leave a place, thing, or person, usually forever.
Abandon
(n) the number of people living in a particular country, area, or place.
Population