1. Unit 2 Earth’s History and Unit 3 Minerals and Rocks

3. Uniformitarianism vs. Catastrophism
Uniformitarianism: geologic processes of the past can be explained by current geologic processes. (gradual over time)
Catastrophism: states that geologic change occurs suddenly (rare occurrences---asteroid striking the Earth)

5. Modern Geology
A happy medium which explains that both uniformitarianism and catastrophes have shaped the Earth.

6. Relative Dating
Method of determining whether an event or object is older or younger than others

7. Law of Superposition
States that younger rocks lie above older rocks

8. Absolute Dating
Method of measuring the age of an event in years through radioactive decay and index fossils.

9. Fossils Fossils are preserved remains or traces of living things.
Most fossils form when living things die and are buried by sediments.
The sediments slowly harden into sedimentary rock and preserve the shapes of the organisms.

10. Fossils Fossils provide evidence of how life has changed over time.
Fossils help scientists infer how Earth’s surface has changed.
Fossils are clues to what past environments were like.

11. Index Fossils -only found in one geologic age.

12. Fossils
The fossil record provides evidence about the history of life on Earth. The fossil record also shows that different groups of organisms have changed over time.
Extinction is if an organism no longer exists and will never again live on Earth. (all members of the species has died.)

13. Petrified Wood
Fossils in which minerals replace all or part of an organism.
How does this happen?
Water rich in dissolved minerals seeped into spaces, evaporated, leaving the hardened minerals behind.

14. Molds and Casts
A mold is a hollow area of sediment in the shape of the organism.
(cavity where it was buried)
A cast is a copy of the shape of an organism.
(sediment fills the cavity)

15. Trace Fossils Examples
Trace fossils provide evidence of the activities of ancient organisms.
Examples
A footprint provide clues about the size and behavior, the speed, how many legs it walked on, lived alone or with others.
A trail or burrow can give clues about the size and shape of the organism, where it lived, and how it obtained food.

16. Preservation Materials
Preservation of remains with little or no change.
Preservation material
Tar
The sticky oil that seeps from Earth’s surface. Tar soaks into the organisms bones, preserving the bones from decay.
Amber
The hardened resin, or sap, of trees. The amber seals the organism from the air protecting it from decay.
Ice

17. Preservation Materials

18. Minerals
A mineral is a naturally occurring, inorganic solid that has a definite chemical composition, crystal structure and has physical properties (hardness, luster,etc.).

19. Inorganic
A mineral must be inorganic, or not formed from living thing or the remains of living things.

20. Solid
A mineral is always a solid. Like all solids, a mineral has a definite volume and shape.

21. Chemical Composition A mineral has a definite chemical composition.
A mineral may made of a single pure substance called an element (gold, copper or sulfur)
Most minerals are made of two or more elements chemically combined to form a compound.

22. Crystal Structure
A mineral’s atoms are arranged in a definite pattern repeated over and over again.

23. Formation and Composition of Minerals
Many minerals come from magma, the molten rock beneath the Earth’s surface. When magma cools, mineral crystals are formed. How and where magma cools determine the size of the mineral crystals.
When magma cools slowly beneath the Earth’s crust, large crystals form.
When magma cools rapidly beneath the Earth’s surface, small crystals form.

24. Kinds of Minerals Silicate and Nonsilicate
Silicates contain the elements silicon and oxygen.
Make up 96% of the Earth’s crust.

25. Identifying Minerals
Minerals have certain physical properties that can be used to identify them, such as color, luster, hardness, streak, density, crystal shape, and other special properties.

26. Mineralogist
A person who examines, analyzes, and classifies minerals.

27. Color
Color is easy to observe, however it is unreliable because many minerals can be weathered which hides their color.
Azurite = always blue
Fluorite = four different colors

28. Luster The way a mineral reflects light from its surface.
Certain minerals have a metallic luster, such as silver, copper and gold. (shiny)
Minerals that do not reflect light have a nonmetallic luster, and are described by terms like glassy, pearly, dull and silky.

29. Hardness
The ability of a mineral to resist being scratched is known as its hardness.
Friedrich Mohs, a German mineralogist, worked out a scale of hardness for minerals ranging from 1 to 10.
The number one is assigned to the softest mineral, talc and 10 is assigned to the mineral, diamond.

30. Streak
The color of the powder scraped off a mineral when it is rubbed against a hard rough surface is called its streak.

31. Cleavage and Fracture
Some minerals, like halite, break into small cubes.
Micas cleave along one surface, making layers of thin sheets. Most minerals do not break along smooth lines.
The terms cleavage and fracture are used to describe the way a mineral breaks.
Cleavage is the tendency of a mineral to split along smooth, definite surfaces.

32. Cleavage and Fracture

33. Special Properties
Some minerals can be identified by special properties.
Magnetite is naturally magnetic.
Fluorite glows under ultraviolet light.
Halite tastes salty.
Sulfur smells like rotten eggs.
Calcite fizzes when hydrochloric acid is added to, double refraction
Uraninite is radioactive.

34. Rocks A rock is a hard substance composed of one or more minerals.
A rock can also be made of or contain naturally occurring substances that do not perfectly fit the definition of a mineral.

35. Types of Rocks
Geologists place rocks into three groups according to how they form: igneous, sedimentary and metamorphic.

36. Rock Cycle
The continuous changing of rocks from one kind to another over long periods of time is called the rock cycle. The rock cycle has no definite sequence. It can follow many different pathways.

38. Igneous Rocks
Igneous rocks were originally hot, fluid magma within the Earth. Igneous get their name from the Latin word, ignis, which means “fire”.

39. Granite and the Rock Cycle
Because granite is made of hard materials it is resistant to nature’s forces. It can be slowly worn down until bits of granite flake off and fall in streams and are eventually reduced to sand. The sand from granite, along with other sediments is carried to the sea and is deposited on the floor. The weight of layers piling on puts pressure on lower layers and with calcite the granite becomes part of a sedimentary rock. After many years, under great pressure and temperature the sedimentary rock will change to a metamorphic rock, quartzite.

40. Fluid and Fire: Igneous Rocks
Igneous rocks are classified according to their composition and texture.
Composition refers to the minerals of which rocks are formed.
Texture means the shape, size, arrangement and distribution of the minerals that make up rocks.

41. Magma Formation Why will rocks melt? Intense heat Extreme pressure
Adding a fluid which lowers the melting point
Partial melting: process by which different minerals in a rock melt at different temperatures

42. Igneous Rock Textures
Some igneous rock textures: glassy, fine-grained, coarse-grained.

43. Glassy Igneous
Glassy igneous rocks are shiny and look like glass. The minerals that make up a glassy igneous rock are not organized into crystals. Obsidian has a glassy texture.

44. Fine-Grained Igneous
Fine-grained rocks, unlike glassy rocks, are made of interlocking mineral crystals.
These crystals are too small to be seen without the help of a microscope.
The dark gray rock known as basalt has a fine-grained texture.

45. Coarse-Grained Rock
Coarse-grained rocks, such as granite, consist of interlocking mineral crystals, which are all roughly the same size and visible to the unaided eye.

46. Igneous Variety
Where and how magma cools determines the size of mineral crystals. The longer it takes magma to cool, the larger are the crystals that form. Glassy and fine-grained rocks form from lava that erupts from volcanoes and hardens on the Earth’s surface. Coarse-grained rocks form from molten rock that cools and hardens within the Earth.

47. Extrusive Rocks Rocks formed from lava are called extrusive rocks.
Lava is brought to the surface by volcanoes, extrusive rocks are also known as volcanic rocks.
Basalt and obsidian are two kinds of extrusive rocks that are quite solid.
Pumice, another extrusive rock, is filled with bubbles.

48. Extrusive vs. Intrusive Rocks

49. Intrusive Rocks
Igneous rocks formed deep within the Earth are called intrusive.
They form when magma forces its way upward into preexisting rocks and then hardens.

52. Sedimentary Rock
Most sedimentary rocks are formed from particles that have been carried along and deposited by wind and water.
These particles, or sediments, include bits of rock in the form of mud, sand or pebbles. Sediments also include shells, bones, leaves, stems and other remains of living things.
Over time they are pressed together to form rocks.

53. Slowly Built Layers: Sedimentary Rocks
The most widely used classification system for sedimentary rocks places them into three main categories according to the origin of the materials from which they are made.
These three categories are: clastic rocks, organic rocks and chemical rocks.

54. Clastic Rocks
Sedimentary rocks that are made of the fragments of previously existing rocks are known as clastic rocks.
Clastic rocks are further classified according to the size and shape of the fragments in them.

55. Conglomerates
Some clastic rocks are made of rounded pebbles cemented together by clay, mud or sand.

56. Sandstones
Clastic rocks made of small, and-sized grains are called sandstones.
In a sandstone, the grains are cemented together by minerals that harden.

57. Organic Rocks Organic rocks come from organisms.
Deposits of limestone may be formed from the shells of creatures when they die. Creatures may also cement their shells together and over time form reefs.
Coal is also made from the remains of living things. It is made from plants that lived millions of years ago.

58. Chemical Rocks
Some sedimentary rocks are formed when a sea or lake dries up, leaving large amounts of minerals that were dissolved in water.
Examples of chemical rocks formed this way include rock salt and gypsum.
Some limestone rocks are formed by inorganic processes in caves. As water evaporates, a thin deposit of limestone is left behind.

60. Metamorphic Rocks
Metamorphic rocks are formed when chemical reactions, tremendous heat and great pressure change existing rocks into new kinds of rocks.

61. Changes in Form: Metamorphic Rocks
When already existing rocks are buried deep within the Earth, tremendous heat, great pressure and chemical reactions may cause them to change into different rocks with different textures and structures. The changing of one type rock into another as a result of heat, pressure and /or chemical reactions is called metamorphism.

62. Metamorphic Rocks
Metamorphic rocks may be formed from igneous, sedimentary or metamorphic rocks.
Heat and pressure are great enough to make rock undergo change.
Temperatures of 100 degrees to 800 degrees cause some minerals to break down.

63. Metamorphic Classification
Like igneous and sedimentary rocks, metamorphic rocks can be classified according to texture. The classification for metamorphic rocks are based on the arrangement of the grains that make up the rocks.

64. Regional Metamorphism
A change in texture, structure, or chemical composition due to a change in temperature or pressure over a large area (tectonic plates)

66. Foliated Rocks
In the first group, the mineral crystals are arranged in parallel layers, or bands.

67. Unfoliated Rocks
In the second, smaller group of metamorphic rocks, the rocks are not banded and do not break into layers.
These rocks are said to be unfoliated.

68. Contact Metamorphism
A change in texture, structure, or chemical composition due to contact with magma.