Main Idea and Summary

Grade 5 Reading Worksheet - Challenge Me

Circle the answer.

1. Read this first

   Why Mexico City Is Sinking

   Mexico City is one of the largest cities in the Americas, with more than twenty million people in its metropolitan area. It is also one of the fastest-sinking cities on Earth. In some neighborhoods, the ground drops more than 30 centimeters every year. Over the past century, parts of the city have sunk more than ten meters.

   The problem begins with the city's unusual history. Mexico City stands on the bed of an ancient lake. Hundreds of years ago, the Aztec capital, Tenochtitlan, rose on an island in Lake Texcoco. After Spanish settlers arrived in the 1500s, the lake was slowly drained so the city could spread. Beneath the streets today lies thick, soft clay that once formed the lakebed. This clay is full of water, like a soaked sponge.

   As the city grew, it needed enormous amounts of water. The easiest source was right underneath it. Engineers drilled wells and pumped groundwater up from the layers below the clay. Today, much of the city's water still comes from these wells. But when water is pulled out, the clay above it dries and squeezes together. A squeezed sponge takes up less space, and so does dried clay. The ground on top sinks lower.

   The sinking causes serious problems. Because the ground does not sink evenly, some buildings tilt. The great cathedral in the city center has leaned for years, and workers have spent much effort to steady it. Water pipes crack as the soil shifts beneath them, so a large share of the city's water leaks away before it reaches homes. Then the city must pump even more water from the ground, which makes the sinking worse. Some streets have dips and cracks. In low areas, rainwater collects and floods neighborhoods. Repairing all this damage costs the city large sums of money every year.

   The squeezed clay cannot simply spring back. Once its tiny spaces collapse, they stay closed, even if water returns. That means the city cannot undo the sinking that has already happened. It can only slow what comes next.

   People are trying several ways to do that. The city is repairing leaky pipes, so less water needs to be pumped. Some neighborhoods collect rainwater on rooftops during the wet season. Engineers are also building systems that let rain soak back into the ground instead of rushing into drains. Some new parks are shaped to hold rainwater like shallow ponds until it sinks into the soil. Other cities that pump groundwater, such as Jakarta in Indonesia, face the same challenge and watch Mexico City closely.

   Mexico City's story shows how a city's past and its daily needs can be tied together. Choices made centuries ago, and water used every day, shape the very ground people stand on.

2. 1.

   The text develops more than one main idea. Which choice names them best?

   • The great cathedral leans, and some streets have dips, cracks, and floods after rain.
   • Mexico City was built where Tenochtitlan stood, and it now has over twenty million people.
   • Pumping water from old lakebed clay sinks the city, causing damage people can only slow.
   • Jakarta and Mexico City both get water from deep wells and watch each other closely.
3. 2.

   How do the second and third paragraphs work together?

   • One names a problem; the other says the problem has been solved.
   • One describes the Aztecs; the other describes modern buildings.
   • One gives facts; the other gives the author's personal opinions about the city.
   • One explains the soft clay; the other explains how pumping squeezes it.
4. 3.

   Which detail best shows that the sinking can make itself worse?

   • The cathedral has leaned for years in the city center.
   • Leaking pipes force the city to pump even more groundwater.
   • Some neighborhoods collect rainwater on their rooftops.
   • Rainwater collects in low areas and floods neighborhoods.
5. 4.

   Why does the author compare the clay to a sponge?

   • to show that the clay can soak up rain again
   • to describe the color and feel of the soil
   • to explain why the old lake was drained by settlers long ago
   • to show how removing water makes the clay shrink
6. 5.

   Based on the fifth paragraph, why do the plans in the sixth paragraph only try to slow the sinking?

   • The city prefers to repair pipes before streets.
   • Engineers do not yet know where the water goes.
   • Rainwater is too dirty to put back underground.
   • Collapsed clay stays squeezed even if water returns.
7. 6.

   Which detail is least important for a summary of the whole text?

   • Uneven sinking tilts buildings and cracks pipes.
   • The Aztec capital rose on an island in Lake Texcoco.
   • Fixing pipes and saving rain can slow the sinking.
   • The city pumps much of its water from below the clay.