| A | B |
|---|
| Geology | ___ is the study of how Earth formed and how it changes. |
| studying rocks | Geologists trace the history of Earth by ___. |
| Plants are rooted in the soil and use nutrients from it to make food. Animals get food by eating plants or by eating animals that eat plants. | How do plants & animals depend upon the soil as a source of food? |
| humus | The part of soil formed from rotting animal & vegetable matter that is dark & rich in nutrients is called ___. |
| Rock | ___ is the hard, solid part of the Earth. |
| Salt | ___ is a mineral that has been used since ancient times to give food flavor & keep it from spoiling. |
| ores | Metals such as aluminum, iron, lead, and tin come from rocks called ___. |
| diamonds, rubies, sapphires, opals, & turquoise | Some rocks contain valuable nonmetallic minerals such as: |
| Quartz | ___ is a common mineral that can be found in several forms and in all three major kinds of rocks. |
| Igneous | ___ rocks form when hot, molten rock cools and hardens. |
| Sedimentary | ___ rocks are made of layers of loose materials that were once part of older rocks. |
| Metamorphic | ___ rock is formed from other rocks that have been changed by pressure and heat deep within Earth's crust. |
| atmosphere | The ___ contains the air that we breathe and makes life on Earth possible. |
| nitrogen & oxygen | The main gases that make up the atmosphere are ___ & ___. |
| troposphere | The ___ is called the weather layer, because that is where nearly all of the Earth’s weather conditions occur. |
| hydrosphere | The ___ consists of all bodies of water and ice, plus water vapor in the air. |
| lithosphere | The crust and upper mantle of Earth from the surface to about 60 miles down make up the ___. |
| Deltas | ___ form when rivers flow into large bodies of standing water, where their speed and ability to carry sediments are suddenly reduced. |
| Grand Canyon | The ___ was formed by the Colorado River over 6 million years ago. |
| glacier | A ___ is a huge, slow-moving mass of ice that scours valleys & flattens landscapes. |
| Great Lakes | The ___ were formed by huge glaciers. |
| Delicate Arch | Wind erosion sculpted ___ in Utah from a wall of ancient sandstone. |
| fossil | A ___ is the mark or hardened remains of a plant or animal that lived long ago. |
| to learn what Earth was like millions of years ago | Why do scientists study fossils? |
