A Unique Texas Treasure

Use a dictionary or thesaurus to define the word arid.

• a flooded, wetland area

• the curve an object takes while in motion

• a specific portion of a larger area

• an area with little to no precipitation

Which words from the paragraph help the reader understand the meaning of arid? (Scroll down to see paragraph).

Did you know that Texas is home to several national parks? These parks celebrate the state's rich natural and historical features. One Texas park is Big Bend National Park, located in the southwestern part of Texas, near Mexico. The park looks to be a mountainous desert, with barren cliffs and dry valleys. Huge rock formations, limestone cliffs, and deep canyons make up some of Big Bend's most dramatic sights. The Rio Grande cuts through the arid landscape, and one of the river's curves gives the park its name. Taking a trip through this geological treasure allows visitors to enjoy natural history firsthand.

• one of the river's curves

• located in the southwestern part of Texas, near Mexico

• a mountainous desert, with barren cliffs and dry valleys

• the state's rich natural and historical features

Which sentence in the introduction paragraph is the thesis? (Scroll down to see paragraph.)

(1) Did you know that Texas is home to several national parks? (2) These parks celebrate the state's rich natural and historical features. (3) One Texas park is Big Bend National Park, located in the southwestern part of Texas, near Mexico. (4) The park looks to be a mountainous desert, with barren cliffs and dry valleys. (5) Huge rock formations, limestone cliffs, and deep canyons make up some of Big Bend's most dramatic sights. (6) The Rio Grande cuts through the arid landscape, and one of the river's curves gives the park its name. (7) Taking a trip through this geological treasure allows visitors to enjoy natural history firsthand.

• 1

• 2

• 4

• 7

What does controlling idea mean?

• main idea

• summary

• closing sentence

• persuasive technique

What is the controlling idea of this paragraph?

But how did fossils of sea creatures come to be in the middle of a desert? Evidence suggests that the land was once not a mountainous desert at all. Instead, geologists, or scientists who study Earth, believe the area was once covered by a shallow, salty sea. Just as we learn about trees by studying the rings in their trunks, scientists examine layers of rock in the ground, called strata, to learn about geological formations. They use these layers to infer what the environment was like during certain periods.

• Geologists use natural evidence to learn how water changed the land.

• Diverse plants and animals live in canyons near the Rip Grande.

• Both trees and rocks make up part of the environment at Big Bend.

• Visitors come to the national park mostly to see rock formations.

Because the Latin root ced means "to go," the reader can tell that the word recede in the following sentence refers to something that --

Eventually, the sea waters receded, and dry land covered more and more of the area that is now Big Bend.

• goes very fast

• falls back or away

• goes again and again

• cannot go any longer

Which information would support the idea that scientists must understand how rock layers are formed to understand how the environment changed?

• They use these layers to infer what the environment was like during certain periods.

• Over time, erosion has helped form narrow canyons along the path of the Rio Grande river.

• Sedimentary rocks, including limestone, sandstone, and shale, contain many different kinds of minerals.

• Evidence suggests that the land was once not a mountainous desert at all.

Which sentence best explains why the Rio Grande river was significant to shaping Big Bend's long-ago natural landscape and development?

• Rafters might see birds like herons, swallows, or kingfishers circle overhead.

• Erosion is the wearing away of land due to wind and water.

• Over time, erosion has helped form narrow canyons along the path of the Rio Grande.

• Plants and animals thrive near the water along the canyon edges.

Scroll to read the following paragraph:

A trip through another group of peaks in the park, the Santiago Mountains, allows park visitors to connect with the region's human history. During the 1700s and 1800s, groups of nomadic Comanche warriors traveled through the Persimmon Gap as they crossed from buffalo-rich lands to the north into what is now Mexico. The Persimmon Gap Visitors' Center, however, is another piece of history. Originally built by a local ranching family in the 1940s, the Visitors' Center used to be a general store.

The author included the information in the paragraph in order to --

• show that human activity has influenced the region around Big Bend

• explain that our understanding of the past doesn't change with new discoveries

• say that visitors should plan to go to ranches and horse trails on their trip

• encourage readers to visit Big Bend National Park and find new fossils

The title of the selection -- A Unique Texas Treasure -- highlights the idea that Big Bend National Park --

• has great natural and historic significance

• contains valuable mineral resources

• is one of the state's many parks

• attracts thousands of visitors each year