The The Richter scaleRichter scale is used to measure earthquake is used to measure earthquake strength.strength.

The Richter scale is The Richter scale is logarithmiclogarithmic.. 7.0 is 10 times stronger than 6.07.0 is 10 times stronger than 6.0 8.0 is 10 times stronger than 7.08.0 is 10 times stronger than 7.0 etc…etc…Therefore 8.0 is Therefore 8.0 is 100 times100 times stronger than 6.0. stronger than 6.0.

Question:Question: An 8.0 earthquake on the Richter An 8.0 earthquake on the Richter

scale releases ___________ times as scale releases ___________ times as much energy as a 2.0 earthquake.much energy as a 2.0 earthquake.

10000001000000

HOW ARE THEY HOW ARE THEY ALL RELATED?ALL RELATED?

Several pieces of Several pieces of evidenceevidence support the support the theory of plate tectonics:theory of plate tectonics:

Africa and South AmericaAfrica and South America were once were once part of a larger continent (called part of a larger continent (called Pangaea)Pangaea)

note note similarities similarities in continental in continental shapeshape

presence of presence of MesosaurusMesosaurus fossils fossils

Earthquakes and volcanoesEarthquakes and volcanoes

occur alongoccur along plate boundaries plate boundaries ****(where one plate is (where one plate is movingmoving relative relative to another) to another)

** Side note** Side noteVolcanoes also occur above Volcanoes also occur above “hot spots” “hot spots”

in the in the middlemiddle of lithospheric of lithospheric plates.plates. The hot spot remains in the same The hot spot remains in the same location while the plate above moves location while the plate above moves

overtopovertop

Magnetism and spreading Magnetism and spreading centrescentres

as plates spread apart, new rock* as plates spread apart, new rock* is formed and is formed and older rock moves awayolder rock moves away from the spreading plate boundaryfrom the spreading plate boundary

* * The rock crystallizes and records the magnetic The rock crystallizes and records the magnetic

field of the earth at that particular timefield of the earth at that particular time

VolcanoesVolcanoes1.1. Composite volcanoesComposite volcanoes - this - this

is the stereotypical volcano, is the stereotypical volcano, erupting and belching smoke erupting and belching smoke and ash everywhere, and ash everywhere, found alongfound along converging converging

plate boundariesplate boundaries Layers of ash and thick lava Layers of ash and thick lava

(magma) form a tall cone.(magma) form a tall cone. As magma reaches the As magma reaches the

surface, it cools, hardens surface, it cools, hardens and traps gases below.and traps gases below.

Pressure builds, eventually Pressure builds, eventually there is an eruption.there is an eruption.

See pages 532 - 534

1.1. Shield volcanoesShield volcanoes - these are - these are NOTNOT found at plate found at plateboundaries, but instead form over boundaries, but instead form over hot spotshot spots (a weak spot (a weak spot in the normal lithosphere). in the normal lithosphere). Flash AnimationFlash Animation

Thin magma/lava flows out from a hot spot and forms a Thin magma/lava flows out from a hot spot and forms a low, wide cone.low, wide cone.

The The Hawaiian IslandsHawaiian Islands are an example of a chain of shield are an example of a chain of shield volcanoes.volcanoes.

3.3. Rift eruptionsRift eruptions - these occur along long cracks in the - these occur along long cracks in the lithospherelithosphere

Not explosive, but release massive amounts of lava.Not explosive, but release massive amounts of lava. Found atFound at divergingdiverging plate boundariesplate boundaries

Classwork:Classwork: Chapter 12 QuizChapter 12 Quiz Chapter 12 Review WorksheetChapter 12 Review Worksheet

Homework:Homework: Workbook Pages 220-221Workbook Pages 220-221