Higgins 
Sinkholes [PDF ebook] 

A sinkhole is exactly what it sounds like: a giant, sinking hole in the earth! They happen in almost every state and every country. They have been carving out Earth’s landscape for millions of years. Learn all about the causes, warning signs, and what to do in case you encounter one of these terrifying and sometimes deadly disasters. This title will allow students to refer to details and examples in a text when explaining what the text says explicitly and when drawing inferences from the text. * Phonetic Glossary * Diagrams and maps * Experiment * Text based questions