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?