88thth Grade Science Grade Science

Unit 8: Unit 8: Changes Over TimeChanges Over Time

Lesson 3: Lesson 3: Forces Behind ChangeForces Behind Change

Vocabulary of InstructionVocabulary of Instruction

1. Asthenosphere1. Asthenosphere

• Is the soft -plastic like- Is the soft -plastic like- layer of the Earth’s layer of the Earth’s mantlemantle on which the on which the lithospheric plates float lithospheric plates float and move around.and move around.

2. Continental Drift2. Continental Drift• The theory that all continents were once connected in a The theory that all continents were once connected in a singlesingle

large landmasslarge landmass that broke apart about 200 million years ago that broke apart about 200 million years ago and and drifted slowly to their current positionsdrifted slowly to their current positions..

• German scientist Alfred Wegener was the first to come up with German scientist Alfred Wegener was the first to come up with this theory.this theory.

3. Convergent Boundary3. Convergent Boundary• A plate boundary where two plates move A plate boundary where two plates move towardstowards each other each other

and collide. and collide. • The plate collisions that occur in these areas can produce The plate collisions that occur in these areas can produce

earthquakesearthquakes, , volcanic activityvolcanic activity, and , and crustal deformationcrustal deformation..

4. Divergent Boundary4. Divergent Boundary• A plate boundary where two plates move A plate boundary where two plates move awayaway from each other, from each other,

forming either mid-oceanic ridges or rift valleys.forming either mid-oceanic ridges or rift valleys.• Divergent boundaries between oceanic plates form submarine Divergent boundaries between oceanic plates form submarine

mountain range such as the mountain range such as the Mid-Atlantic RidgeMid-Atlantic Ridge; ; volcanic volcanic activityactivity in the form of fissure eruptions; shallow in the form of fissure eruptions; shallow earthquake earthquake activityactivity; creation of ; creation of new seafloornew seafloor and a and a widening ocean basinwidening ocean basin. .

5. Erosion5. Erosion

• Process in which Process in which surface materialssurface materials (fragments of (fragments of rocks and soil) are rocks and soil) are worn away and transported worn away and transported from one place to anotherfrom one place to another by agents such as by agents such as gravity, water, wind, and glaciersgravity, water, wind, and glaciers..

6. Land Subsidence6. Land Subsidence • The The sinkingsinking or or subsidingsubsiding of land surface as a result of land surface as a result

of geologic processes or human activities.of geologic processes or human activities.

7. Lithosphere7. Lithosphere• Solid and rigid layer of Earth consisting of the Solid and rigid layer of Earth consisting of the crustcrust and part and part

of the of the upper mantleupper mantle. It is about 100 km thick.. It is about 100 km thick.

• The lithosphere is The lithosphere is brittlebrittle enough at some locations enough at some locations to to fracturefracture and and produce earthquakesproduce earthquakes..

8. Mid-Ocean Ridge8. Mid-Ocean Ridge• Area where Area where new ocean floor is formednew ocean floor is formed when lava when lava

erupts through cracks in the Earth’s crust.erupts through cracks in the Earth’s crust.• It is a It is a divergent plate boundarydivergent plate boundary..

9. Neap Tide9. Neap Tide• A tide with the A tide with the least differenceleast difference between low and high tide that between low and high tide that

occurs when the occurs when the EarthEarth, , moonmoon and and sunsun are arranged are arranged perpendicularperpendicular to each other (pull at to each other (pull at right anglesright angles to the Earth). to the Earth).

• Neap tide comes Neap tide comes twice a monthtwice a month, in the , in the firstfirst and and thirdthird quarters of quarters of the moon.the moon.

10. Pangaea10. Pangaea• The The large ancient landmasslarge ancient landmass that was composed of the that was composed of the

entire entire continents joined togethercontinents joined together that broke apart 225 that broke apart 225 million years ago and million years ago and gave rise to today’s continentsgave rise to today’s continents..

11. Plate Tectonics11. Plate Tectonics

• The theory that The theory that Earth’s Earth’s crustcrust and and upper mantleupper mantle are broken into plates are broken into plates that that floats and movefloats and move around on a plastic like around on a plastic like layer of the mantle.layer of the mantle.

12. Sea-Floor Spreading12. Sea-Floor Spreading• Hess’s theory that Hess’s theory that new new

seafloorseafloor (oceanic crust) (oceanic crust) is formed when is formed when magna magna is forced upwardis forced upward toward the surface at a toward the surface at a mid-ocean ridge.mid-ocean ridge.

13. Spring Tide13. Spring Tide• A tide with the A tide with the greatestgreatest difference between high and low tide difference between high and low tide

that occurs when the that occurs when the EarthEarth, , moonmoon and and sunsun are arranged in a are arranged in a straight line, during the straight line, during the newnew and and full moonfull moon phases. phases.

• Spring tides happen Spring tides happen twicetwice a month. a month.

14. Transform Boundary14. Transform Boundary • A plate boundary where two tectonic plates slide, grind, and A plate boundary where two tectonic plates slide, grind, and

past each other in past each other in oppositeopposite directions along a transform fault. directions along a transform fault. (also known as (also known as transform fault boundarytransform fault boundary, , sliding boundarysliding boundary, , or or conservative plate boundaryconservative plate boundary).).

• San Andres FaultSan Andres Fault in California is an example of transform in California is an example of transform boundary.boundary.

15. Uplift15. Uplift

• This process result from This process result from convergent boudariesconvergent boudaries where land is being where land is being raised to a higher raised to a higher levellevel, as during a period , as during a period of mountain building. of mountain building.

• Examples of mountain Examples of mountain ridges include the ridges include the RockiesRockies and the and the HimalayasHimalayas..

16. Volcanic Mountains16. Volcanic Mountains• Mountains formed when Mountains formed when

molten -lava rock-molten -lava rock- and other and other volcanic material volcanic material reaches the reaches the Earth’s surfaceEarth’s surface through a through a weak crustal area and piles up weak crustal area and piles up into a into a cone shaped structurecone shaped structure..