Question

“satellite monitors rain that triggers landslides” by nasa earth observatory

1. on february 17, 2006, the village of guinsaugon on leyte island in the philippines disappeared. after several days of unusually heavy rain, a massive landslide swallowed more than 350 houses and an elementary school, burying more than 1,100 people. residents of the village, situated at the foot of a mountain, had no warning.
2. landslides occur everywhere in the world, but the danger of rainfall - induced slides tends to be much greater in tropical mountainous regions like those in the philippines, central and south america, and southeastern asia. steep terrain and heavy tropical rains put dense populations at risk. monitoring landslide - producing conditions typically requires extensive networks of ground - based rain gauges and weather instruments. but many of the developing countries in high - risk areas lack the resources to maintain such systems; heavy rains and flooding often wash away ground - based instruments.
3. robert adler, a senior scientist in the laboratory for atmospheres at goddard space flight center, and yang hong, a research scientist at goddard earth sciences technology center, are confronting the problem by developing a satellite - based system for predicting landslides. the system makes data available on the internet just a few hours after the satellite makes its observations. adler said, “if we can complete this ‘real - time’ product and make it available on the web, then almost any government or organization in the world can access this information.”

mapping landslide susceptibility

1. satellite is the key factor in adler and hongs product, but first, they needed to piece together a global landslide susceptibility map, which would help reveal terrain and ground properties. hong said, “satellite can be a trigger for landslides, but ground conditions are also very important.”
2. adler and hong mapped topography, as well as the direction that rivers and runoff would flow.

part a
where does the central idea regarding the usefulness of satellites begin to emerge?

• in paragraph 1 when the author describes the devastation caused by a landslide in 2006
• in paragraph 2 when the author emphasizes the problems related to maintaining ground tools
• in paragraph 3 when the author identifies the goals of adler and hongs scientific research
• in paragraph 4 when the author describes the landslide map constructed by adler and hong

Explanation:

The article starts by describing a devastating landslide in 2006. Then in paragraph 3, it introduces scientists Adler and Hong who are developing a satellite - based system for predicting landslides, which is where the idea of satellite usefulness emerges.

Answer:

In paragraph 3 when the author identifies the goals of Adler and Hong's scientific research