¿Por qué hibernan los animales? (Why Animals Hibernate)

The rock cycle has been taking place for millions of years. However, geologists have only known about this phenomenon for about 300 years. Young terrestrial explorers are introduced to different types of rocks, where in the cycle these rocks fit, and where in Earth's layers each step takes place. Fact boxes provide readers with fun additional information. A diagram helps readers make sense of the new information they're learning.

When rocks change because of environmental conditions, the new rocks are called metamorphic rocks. A rock's chemical or physical makeup may change because of conditions such as temperature, stress, or pressure. Your readers will learn fascinating facts including where metamorphic rocks are most commonly found, the different types of metamorphism, and how metamorphic rocks are identified. Full-color photographs depict these rocks in nature. A helpful graphic organizer shows how these fascinating rocks form.

Although Earth is mostly made up of igneous and metamorphic rock, sedimentary rock covers about 75 percent of Earth's land surface. This means it's the most visible kind of rock on Earth. Sedimentary rocks form when sediment accumulates and compacts. Your readers will learn how sedimentary rocks form, the different types of sedimentary rocks, and how people use sedimentary rocks. Fun fact boxes provide readers with additional information. A helpful diagram illustrates how sedimentary rocks form.

A teen is trapped in an abusive relationship, and a friend wants to help. This comprehensive book shares how to spot the warning signs of an abusive relationship, how to be supportive of a friend who needs help, and what kind of resources are available to both the helper and the victim. It may be scary to deal with a friend in an abusive situation, but this informative guide will be a strong tool in letting readers know how practical ways that they can navigate a difficult situation and give their much-needed support.

People today refer to the Midwestern and prairie states as flyover country. During the Civil War, crossing those areas was the biggest obstacle in uniting the East and West Coasts of our divided nation. An act of Congress in 1862 authorized the Central Pacific and the Union Pacific railroad companies to build a railroad that would link the coasts. Seven years later, on May 10, 1869, an overwhelmingly immigrant labor force completed the task when a rail line was join in Promontory, Utah. The states had become united at last.

El Frente Polisario pretende crear un estado independiente en el Sahara Occidental. La comunidad internacional no puede aceptar una idea asi. Ese pretendido estado, situado en el limite occidental del Sahel, seria penetrado con gran facilidad por Al Qaeda en el Magreb Islamico junto a sus grupos secuaces dedicados a actividades criminales internacionales organizadas. Frente a ello la propuesta del Reino de Marruecos de un Estatuto de Autonomia, se ofrece como la mejor solucion, especialmente desde la perspectiva de la seguridad internacional, y responde a los anhelos de la poblacion Saharaui. ...

¿Chocolate o vainilla? ¿Dulce o salado? ¿Gatos o perros? Cuando de ciertos temas se trata, todo niño tiene sus preferencias. Desde que existen las mascotas, el debate entre tener un gato y tener un perro ha sonado fuerte durante los recreos y almuerzos en todos los colegios del mundo. ¿Cuál es mejor? ¿Cuál es más inteligente? Este libro presenta los hechos de manera divertida e informativa. A los niños les encantará leer este texto de Nivel 3 para decidir cuál es la respuesta a la pregunta eterna - ¿gatos o perros? NationalGeographic apoya a los educadores K-12 con Recursos del...