geology
- the study of the materials of the earth's crust
crust
- the outer layer of the Earth, from 5 to 60km thick
mineral
- a solid element or compound that occurs naturally in the earth's crust
elements
- a pure substance that cannot be broken down, contains one king of particle (ex: gold, silver)
compounds
- a pure substance that contains 2 or more elements (ex: quartz; contains silicon and oxygen)
Minerals
- the building blocks of rocks
- approximately 3000 different minerals
Properties of Minerals
property
- the characteristic of a material (ex: color, density, luster, etc.)
Properties used in Mineral Indentification
1. Color
- describes what the mineral looks like (ex: sulphar - yellow)
2. Lustre
- how the light strikes the surface of the mineral (ex: quartz - glassy, pyrite - metallic)
3. Hardness
- a rating scale of one (softest) to ten (hardest)
| Rating and Equivelant Mineral | Someting to Compare to | |
| 1. talc | Softest | Soft pencil point |
| 2. gypsum | fingernail | |
| 3. calcite | copper coin | |
| 4. fluorite | ||
| 5. apatite | Pocket-knife blade | |
| 6. feldspar | steel file | |
| 7. quartz | sandpaper | |
| 8. topaz | ||
| 9. corundum | emery paper | |
| 10. diamond | Hardest |
4. Streak
- the powdery mark left when a mineral is scratched across a tile (ex: hematile - reddish brown)
5. Crystals
- the distinctive geometric design that is unique to each crystal in a mineral
6. Cleavage
- the tendency of a crystal to split easily along a plane parallel to its flat sides or forces
7. Fracture
- minerals that have no cleavage, break into rough uneven fragments
8. Other:
a) Magnetic - minerals that contain iron are attracted to a magnet (ex: magnetite)
b) Smell - what it smells like (ex: sulphur smells like eggs)
c) Acid Test - minerals that contain calcium carbonate fizz
rock
- the basic material of the earth's crust
magma
- hot molten rock found below the surface
lava
- hot molten rock that flows
There are 3 types of rocks:
1. ingneous rock:
- rocks that are formed by the cooling of magma
- 2 types of igneous rocks: instrusive and extrusive
Instrusive
- formed from magma that cools below the surface
- the mamga cools slowly; large crystals form
- plutonic
- ex: granite, gabbro
Extrusive
- formed from lava that cools quickly above the surface
- the lava cools rapidly; small crystals or none formed
- volcanic
- ex: obsidian, pumice, basalt, rhyolite
2. sedimentary rock
- rocks that are formed from the accumulation of sediments
- sediments produced by weathering, erosion, desposition, precipitation and lithification
- ex: sandstone (cemented sand), shale (cemented clay), conglomerate (rounded pebbles cemented together), limestone (solidified mud)
Flow chart of formation
1. Tiny pieces are broken off by weathering and erosion
2. Sediments mored by wind, water or ice and are deposited
3. Sediments in the water settle at different rates
4. Sedimetary rocks are formed when the water evaporates leaving solid materials behind
5. Soft sediment becomes rock by a process called lithification where the rocks get compacted, dried or cemented together
3. metamorphic rock
- rocks that are formed below the earth's surface when the rock is altered by heat, pressure and/or chemical reactions
- they are altered igneous and sedimentary rock
parent rock
- a rock that becomes altered to a form a metamorphic rock
| Parent Rock | Metamorphic Rock |
| limestone | marble |
| sandstone | quartzile |
| shale | slate |
| granite | gneiss |
The Rock Cycle
- a complicated network of natural changes that result in the formation of three different rock types
Summary
1. All rock types can melt into magma.
2. When magma recrystallizes below the surface - igneous intrusive rocks are formed. When lava cools quickly on the surface - igneous extrusive rocks are formed.
3. All rock types on the surface become sediments by weathering and erosion. The loose sediments become desposited and cemented together to form sedimentary rock.
4. All rock types can recrystallize and change into metamorphic rock by being exposed to high temperatures and pressure.
NOTE: Any rock can be changed to another form under the right conditions.
absolute age
- an exact age, which can be given years or in fractions of years (ex: I am 15 years old today)
relative age
- the age of something compared with the age of something else (ex: before I was born, TV was invented)
priciple of superposition
- any sedimentary rock in a horizontal selection of layered rock is considered younger that the rock below it
|//////////| youngest |**********| ^ |~~~~~~~~~~| ^ |,.,.,.,.,.| oldest
fossils
- any organism or trances of an organism that once existed
- 5 kinds of fossils
actval remains
- remains of organisms may be found frozen in ice, in amber or may be mummified (ex: fly in amber)
moulds (or imprints)
- a cavity made by the imprint of an organism; the shape is preserved (ex: footprint)
casts
- sediments fill in the mould and harden; showing the orginal form of the organsim (ex: trilobite)
tracks (or trails)
- footprints, burrows, or trails show the activity of an organism
petrified parts
- remains turned to stone; minerals fill the shape of the organsim (ex: petrified stone/wood)
- Fossils are only found in sedimentary rocks
- The fossils would be destroyed by heat and pressure or by melting, therefore they would not be found in metamorphic or igneous rock
- Fossils represent a limited sample of all life forms that existed on earth
Conditions nessary to preserve organisms as fossils
1. Hard body parts
2. Number of organisms
- the greater the number that existed, the greater the chances of finding them
3. Quick burial; to preserve the organism before it decays
Dating Fossils and the Geological Time Scale
- Scienctists are able to date the age of rocks by teh presence or absence of specific fossils; or index fossils
- The sequence of fossils allows us to trace events that have occured in the Earth's geological history
radioactive dating
- the process of using a radioactive element to find the age of the object
- the Geological Time Scale is a scale that shows us the events that occured in the Earth's geological history
- there were 4 main eras; precambrian, paleozoic, mesozoic, cenozoic
era
- unit of time in the geological time scale
- different eras last for different times
- each one is unique
| Era | Millions of years ago | Fossil Record of Major Changes in Life on Earth |
| Cenozoic | 65 to present | - appearance of most modern species - many more species of mammals - first grasses - first human-like species |
| Mesozoic | 225 to 65 | - many more species of plants, birds, and mammals - dinosaurs flourish and then become extinct - first flowering plants - first birds and mammals |
| Paleozoic | 600 to 225 | - first reptiles - first large land animals (amphibians) - first insects - first large land plants - first fish with jaws |
| Precambrian | 4600 to 600 | - first soft-bodied animals (those without backbones) - first simple organisms (bacteria) - formation of the Earth |