Lesson 2 Reading Guide - Vocab

1. The Geosphere • mantle • lithosphere • asthenosphere • core • luster • streak • cleavage • fracture • crust Lesson 2 Reading Guide - Vocab

2. Materials in the Geosphere • The basic building blocks for soil, rocks, and metals are minerals. • Minerals combine in different ways, forming the other materials in the geosphere. Lesson 2-1

3. Materials in the Geosphere • A mineral is a naturally occurring, inorganic solid with a crystal structure and definite chemical composition. • Properties such as color, crystal shape, luster, streak, hardness, cleavage, and fracture can be used to identify minerals. Mark Schneider/Getty Images Lesson 2-1

4. Materials in the Geosphere(cont.) • Luster is the way a mineral’s surface reflects light. • Streak is the color of a mineral’s powder. It is observed by scratching a mineral across a tile of unglazed porcelain. • Thehardnessof a mineral can be ranked on a scale of 1 to 10 on the Mohs scale, with 1 being the hardest. DEA/A.RIZZI/Getty Images Lesson 2-1

5. Materials in the Geosphere(cont.) • Cleavage is the tendency of minerals to break along smooth, flat surfaces. • Fracture is the tendency of minerals to break along irregular surfaces. • Some minerals tend to break apart and combine with other substances, while other minerals are more stable and durable. Lesson 2-1

6. Materials in the Geosphere(cont.) • A rock is a naturally occurring solid composed of minerals and other materials. • Rocks are classified according to how they form. • The three main types of rocks are igneous, metamorphic, and sedimentary. Lesson 2-1

7. Earth systems interact in the rock cycle. Lesson 2-1

8. Materials in the Geosphere(cont.) • Igneous rock forms when molten rock material cools and hardens. • Metamorphic rock forms when sedimentary, igneous, or other metamorphic rocks are subjected to high temperatures and extreme pressure. • Sedimentary rocks form when sediment is eroded by water, wind, ice, or gravity and deposited in layers. Lesson 2-1

9. Materials in the Geosphere(cont.) • The formation of sedimentary rocks involves interactions among all Earth systems. • Rocks can be broken down by physical and chemical weathering. Lesson 2-1

10. Soil is the loose, weathered material in which plants grow. Lesson 2-1

11. Soil layers form as rock is slowly transformed into soil. • Soil formation begins when rocks weather into sediment and water dissolves minerals and other materials from the sediment. Lesson 2-1

12. Materials in the Geosphere(cont.) • Wastes from organisms and the decaying bodies of dead organisms provide soil with nutrients that makes it more fertile. • A major part of the organic matter in soil is carbon that plants obtain from the atmosphere through photosynthesis. • Soil plays a major role in the phosphorus and carbon cycles. Lesson 2-1

13. Interactions among all Earth systems take place in soil because soil contains minerals, water, air, and organisms, all in close contact. Lesson 2-1

14. Structure of the Geosphere • The geosphere has three main layers: the crust, the mantle, and the core. • The densest layer of the geosphere is the center, or core, and the least dense layer is the outer crust. Lesson 2-2

15. Structure of the Geosphere(cont.) • Scientists hypothesize Earth’s layers formed early in the planet’s history. • Ancient Earth was much hotter than it is today and thermal energy melted some of the rock. • Gravity pulled denser materials through the melted rock toward Earth’s center, forming layers. Lesson 2-2

16. Structure of the Geosphere(cont.) • Each of Earth’s layers has a different density. • Most of the geosphere is made of solid rock, but some of it is made of metal. Lesson 2-2

17. Structure of the Geosphere(cont.) • Scientists know about the makeup of Earth’s deep inner layers from gathering data by analyzing earthquake waves. • When the waves travel through Earth, they change speed and direction when they pass through materials with different densities. Lesson 2-2

18. The crustis the thin outer layer of the geosphere. • Oceanic crust is made of the dense igneous rocks basalt and gabbro. Lesson 2-2

19. Continental crust, which is thicker but less dense than oceanic crust, is made of igneous, metamorphic, and sedimentary rock. Lesson 2-2

20. The mantleis the thick, rocky middle layer of the geosphere. • The mantle has the largest volume of any layer of Earth, and much of it is made of the rock peridotite. Lesson 2-3

21. The crust and the uppermost mantle form a brittle outer layer called the lithosphere. • The weak, partially melted layer of the mantle is called the asthenosphere. Lesson 2-3

22. Structure of the Geosphere(cont.) • The dense, metallic center of Earth is called the core. • The core is made mainly of iron with some nickel and traces of other elements. • Due to the high temperatures near the center of the Earth, the outer layer of the core is liquid. Lesson 2-3

23. Scientists theorize that the movement of liquid iron in the outer core produces Earth’s magnetic field. Lesson 2-3

24. Structure of the Geosphere(cont.) • Inside the outer core is a sphere of solid metal. • Despite the scorching heat, the metal in the inner core is not melted. • The high pressure from the masses of all Earth’s layers compresses the inner core, making it solid. Lesson 2-3

25. Minerals are the basic building blocks for materials in the geosphere, including soil, rock, and metal. • The three main layers of the geosphere are the crust, the mantle, and the core. Lesson 2 - VS

26. The layers of the geosphere have different densities and chemical compositions. Lesson 2 - VS

27. What is the color of a mineral’s powder, observed by scratching a mineral across a tile of unglazed porcelain? A. cleavage B. fracture C. luster D. streak Lesson 2 – LR1

28. What is the loose, weathered material in which plants grow? A. mantle B. soil C. geosphere D. rock fragments Lesson 2 – LR2

29. What is the weak, partially melted layer of the Earth’s mantle? A. asthenosphere B. core C. lithosphere D. oceanic crust Lesson 2 – LR3

30. Do you agree or disagree? 4. The inside of Earth is mostly solid rock. 5. Rock makes up minerals. 6. Living things help make soil. Lesson 2 - Now