Earth borers

"Earth borers are huge, amazing tools that help build tunnels. Readers will dig deep underground with these massive machines to learn how they chew up rocks and dirt and help engineers build new things far below Earth's surface . . . full-color photographs showcase these large borers and the tunnels they create, which are used by cars, trucks, and even trains to take people from place to place. . . . also looks at the environmental impact these machines have on our lives and potential problems they cause, such as sinkholes"--Publisher.