esci 215 chapter 15. the formation of the earth earth was a ball of molten (liquid) rock lighter...
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Earth (Geology)ESCI 215
Chapter 15
The Formation of the EarthEarth was a ball of molten (liquid) rock
Lighter material floated to the topHeavier material settled lower down
Earth cooled and hardenedBasalt rock is heavy and usually found in
Earth’s crust under oceansGranite is a lighter rock and usually found in in
Earth’s crust on mountains
The Structure of the Earth
The Earth’s layers:Crust
Approximately 8 – 64 km thick solid rock and other material that floats on the mantle Thinnest under oceans and thickest on landmasses
Mantle Approximately 2900 km thick Semisolid rock
Core Approximately 3500 km in diameter Mostly molten rock (lava)
Earth’s TemperatureThe temperature of the Earth increases the
closer you are to the core. An 1800m deep mine shaft would be 55°C warmer than at the surface. Temperature increases 1°C for every 33m. Why?Molten rock near core is very hotPressure increases as you move further into
the Earth; increasing pressure increases the temperature
How do we know the Earth has Layers?Sound Waves:Sound waves (i.e. produced through
explosions) travel through layers of the Earth differentlySpeed of sound wave changes depending on
the layerSound waves are refracted when they hit the
mantle at an angle (similar to light refraction)Scientist study the echoes of the reflected
sound waves
How do we know the Earth has Layers?Earthquake Shock Waves:Earthquake shock waves travel through the
layers of the Earth differentlyPrimary wave - a longitudinal (push-pull) wave that
travels through the mantle and core and is detected all over the planet
A transverse (side-to-side) wave cannot travel through the liquid core and so it is not detected all over the planet
See Fig 15.3 on page 284 in textScientists can calculate the diameter of the core by
studying the where the transverse waves do not reach
Surface Features of EarthThe surface features of the Earth are shaped over
time by:Internal forces
Gradual shifting of the earth Erupting volcanoes Earthquakes
Build up of sedimentExternal forces
Movement of glaciers over the Earth Carve valleys and flatten mountains
Erosion and weathering
Tectonic PlatesEarth’s crust is made up of 8 major and many
minor tectonic platesAfrican plate, Antarctic plate, Indian plate,
Australian plate, Eurasian plate, North American plate, South American plate, Pacific plate
The border between 2 tectonic plates is called a boundary
Tectonic PlatesThese plates move in different ways:
Convergent boundaries – tectonic plates move together Creates mountains and volcanoes
Divergent boundaries – tectonic plates move apart Causes earthquakes and creates trenches
Transform fault boundaries – tectonic plates move along in opposite directions Causes earthquakes
Convergent BoundariesOcean plate pushes into and under continental plate. This lifts the continental plate and forms mountain range.
2 ocean plates converge and one moves under the other. This forms a deep trench in the ocean floor and can also create underwater volcanoes.
2 continental plates converge and one plate is pushed (only a little) under the other . The crust folds and folded mountains are created.
http://www.platetectonics.com/book/page_5.asp
Folded MountainsMountain ranges that are formed when 2 tectonic plates converge
The pressure forces the edges of the plates upward in a series of folds
Most common type of mountain
Examples: Himalayans, Andes, Alps and Appalachians
http://education.nationalgeographic.com/education/encyclopedia/fold-mountain/?ar_a=1
Block MountainsMountains that form when 2 tectonic plates
converge with great forceThe tectonic plates crack and push blocks of
rock up Usually have a steep front side and a sloping
back sideExamples: Sierra Nevada and Harz
mountains
Displacement MountainsIsostatic Adjustments
As the Earth’s crust is weathered away, it becomes lighter and is pushed up from below
The crust bends up and down changing the shape of rocks
This happens constantly to mountains by wind, water, and ice over millions of years
EventsEvent 15-A Geological Maps of Your Area
Students learn how to use maps to learn about the surface features of places
Event 15-B Folded MountainsStudents create folded mountains using clay
and observe how the forces create the mountain shape
Event 15-C Isostatic AdjustmentShows how erosion can cause mountains to
rise
Rocks and MineralsRocks
Organic or inorganic chunks of Earth’s crustCan be made up of similar matter or random
matterUsually composed of 2 or more minerals
MineralsInorganicMade up of specific elements or combinations
of elements
3 Groups of RocksIgneous Rock
Formed from molten matter and contains crystals Size of crystals decrease as the speed of cooling
increasesExamples: basalt, granite, obsidian, pumice
Sedimentary RockFormed as running water carries materials and
deposits them in another location in layersUsually worn smooth by rubbing against other materialExamples: limestone, sandstone, shale, chalk, coal
Metamorphic RockIgneous or sedimentary rock that has been changed
due to extreme heat or pressure Examples: sandstone to quartzite, limestone to marble,
shale to slate
Event 15-F Crystal FormationStudents investigate how the rate of cooling
influences the size of crystals in the rock (igneous rock)
Crystals are larger when the alum cools slowly
Event 15-G Unmix the SoilsShows how sediment settles in layers
(sedimentary rock)
Rocks and Movement of FluidsImpermeable rock
No water can pass through this rock (until it is pierced)
Permeable rockPorous rock that soaks up fluids
Event 15-H Rock SpongesStudents investigate which stones can absorb
fluids
Characteristics of Rocks8 major characteristics used to identify rocks:1. Hardness - Moh’s scale measures a rock’s hardness2. Colour – rocks have different colours3. Streak - The colour of a rock’s powder; found by
dragging in on porcelain4. Texture – size of grains or crystals in the rock5. Luster – how the rock reflects light6. Cleavage – the way the rock breaks when hit by a
hammer7. Chemical – rocks have different chemical properties8. Density – rocks have different densities; found by
weighing rock in air and then in water, calculating the difference, divide the air weight by the difference
Event 15-D Classifying RocksStudents classify rocks from around the schoolUse this Event before students learn about the
8 characteristics used to identify rocks
Event 15-E Scale of HardnessStudents compare hardness of different
materials
WeatheringWeatheringThe slow physical and
chemical breaking down of rocks over time
Caused by wind, water, temperature changes, and chemical action
WeatheringEvent 15-J Dissolving Stones
Students investigate the effects of chemical weathering on limestone
Event 15-K Building Stalactites and Stalagmites Students investigate how stalactites and
stalagmites are formed in caves
Event 15-N force of FreezingStudents investigate how
ice expands in cracks in rocks and breaks it apart (weather)
ErosionErosionThe wearing away of the Earth’s surface
where the matter is transported elsewhereCaused by mostly running water and
somewhat by wind, glaciers, and temperature changes
Erosion is influenced by the speed of water, the slope of the land and the depth of the water
Event 15-L Rock ErosionStudents investigate the erosion of rocks Shaking rocks in a jar simulates the effect of
running water on rocksEvent 15-M Pebble Pinnacles
Shows how hard surface rock protects softer rock underneath from the effects of erosion
SoilsSoil covers most of the EarthFertile soil contains large amounts of minerals Different soils have different sized particles
See Table 15.2 on page 298 in text for classification of soils
Good quality soil contains a mixture of these sizesSize of particles influences permeability of soil
Event 15-o Permeability of SoilsStudents investigate the permeability of different
soil typesEvent 15-P Water Holding Capabilities of Water
Students investigate the ability of different types of soil to hold water (sand, clay, loam)
Soil Conservation Vegetation can only grow in the
top 5 – 10 cm of soilThis thin layer of soil is easily
eroded awayPlant roots help to hold the soil in
place Event 15-Q Erosion on Bare and
Grassy Slopes Shows how grass helps to hold soil
in place by soaking up running water
Event 15-R Check Dams Students build a dam to investigate
how soil is eroded by running water
Filtering WaterEvent 15-S Cleaning Muddy
WaterStudents investigate how
pebble, sand, and coal can be used to filter particles out of water
Caution – students should not drink the “filtered” water because it could still have bacteria
Assessment and InstructionPlan a field trip for students to explore the natural geology
of the places around themBuild on what students have been learning in classInvite an Elder to share their knowledge of the geology and
other knowledgeable community membersStudents could collect and identify rocks or examine how the
landscape has been shaped by erosion and weathering Explain task and your expectations to the studentsObserve students’ conversations about the topic, how they
organize and record their data Ask questions to see their level of understanding and use
of scientific vocabulary Students complete a written report when back in class and
present their findings to the class
WebsitesSee websites listed in text on page 300-301
DiscussionWhere does this topic fit into the Science
curriculum?Which grades and strands?Which curriculum objectives relate to the
discrepant events?