托福阅读official69 The word “hazards”in the passage is closest in meaning to 答案解析【小站备考】

Around 2,500 years ago, Amerindian peoples began to live in settled communities in what is now the southwestern United States, growing maize—a crop unique to the New World—together with squash and, later, beans. These cultures developed advanced technologies that allowed them to manipulate their environment and thrive in its arid conditions, though ultimately environmental factors may also have led to their disappearance.

One of these cultures, the Hohokam, practiced irrigation-based agriculture. Knowledge of Hohokam irrigation systems is based on archaeological remains found in southern Arizona as well as on extrapolation from technologies currently in use. Because the land was desert with less than 10 inches of rainfall a year, agriculture required catchment dams, irrigation canals, and water conservation. Between A.D. 300 and 900, the Hohokam manipulated the arid environment by building large canals, some as wide as 30 feet across, 7 feet deep, and 8 miles long, that could fertilize as many as 8,000 acres at a time with water from the Salt and Gila river systems. The Hohokam could grow crops and store them throughout the year, producing a continual supply of food. An environmental consequence of irrigated agriculture, however, is that water from the rivers leaches out salts, drawing them up from the subsoil and leaving salinated (salty) topsoils. Just as the Mesopotamian settlements of the Near East were abandoned owing to salinization of the land, the Hohokam may have been forced to abandon their villages. Alternatively, they may have remained, evolving and adapting to changed conditions. By the time the Spanish arrived in the region in the sixteenth century, they met Amerindians called Akimel O’odham, who were still practicing a form of irrigation, but not on the enormous scale developed by the Hohokam. Other explanations for the disappearance of Hohokam culture include flooding, drought, earthquakes, and deforestation.

A second group of southwestern peoples, the Anasazi, also developed advanced technologies for manipulating their environment. They constructed large multistoried communal houses in villages, or pueblos, along the edges of a river in the bottom of New Mexico’s Chaco Canyon where they planted crops. The communities consisted of many small villages with larger central cities containing four-story apartments and ramrod-straight roads that linked Chaco Canyon with other communities in the Southwest.

One Anasazi pueblo, Mesa Verde, illustrates the sophistication with which these peoples transformed their environment. Mesa Verde is situated 7,000 to 8,000 feet above sea level on a vast forested plateau into which erosion has cut numerous steep- walled canyons. Mesa Verde culture and agriculture developed gradually over time. The people of the earliest culture, from around A.D 500 to 750, were basket weavers who lived underground in pit houses. Around A.D 750 to 1100, they added ceremonial chambers called kivas and began building houses above ground out of bricks. Between A.D 1100 and 1300, they reached the peak of their complex culture, building ladders ascending to the cliff areas as well as pathways descending to agricultural fields in the valleys. The vast agricultural network covered some 80 square miles of development, supporting numerous pueblos located about 1,800 to 2,000 feet above the river.

Not only did the Anasazi build roads and pueblos, they also put their understanding of astronomy to practical use. In particular, the Anasazi attained the ability to predict the advent of growing and harvesting seasons based on arrival of solstices (longest and shortest days) around June 21 and December 21 and equinoxes (days with equal periods of light and darkness) around March 21 and September 23. They did so by building an observatory on Fajada Butte in Chaco Canyon, a stone-slab structure assembled so that on solstices and equinoxes, a sliver of sunlight entered between two stones and fell on a petroglyph (an image carved onto a rock) in a characteristic way. With this knowledge they gained a measure of control over the hazards of an arid environment.

The Anasazi disappeared from their homeland at the height of their cultural development around the end of the thirteenth century. Deforestation, social disruption， and the onset of an 11-year drought around A.D. 1280 (as evidenced by the narrowness of tree-ring growth) may have been factors leading to the abandonment of the pueblos.

OFFICIAL69 The word “hazards”in the passage is closest in meaning to

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