C1.1 – Structure of the Earth

The Earth is Like an Egg The Earth is separated into layers according to their densities, it can be compared to an egg. Core (like the yolk): inner- most layer with a solid inner core and liquid outer core Mantle (white of the egg): layer between crust and core Lithosphere (shell of egg): outermost rigid layer of rock

Putting it all together crust: lithosphere with oceanic crust and continental crust mantle: includes outer asthenosphere and inner mesosphere liquid outer core solid inner core

Complete the following chart in your notes Earth’s Layers Density Description Thickness (km) Atmosphere Less dense More dense Gaseous 300 very thin, overlaps other crust 4 - 7 solid, most rigid layer 20 - 70 Mantle least rigid (more plastic) layer of mantle 225 – 275 more rigid than upper layer of mantle Core Outer core Inner core

Is this realistic? Trailer from the movie “The Core” Site 3 factually true components from the trailer and 3 completely unrealistic ones.

Motion in the Mantle We can’t directly observe these layers so use indirect evidence like earthquakes to develop theories One theory is that nuclear decay in the core provides the heat energy to cause the flow of material in the mantle Like a hot bowl of French onion soup Hot material rises toward the cheesy crust; cool materials then sinks The effect of this motion is that is cracks, tears and moves the crust This is cycling of heat is called convection

Convection in the Earth The lithosphere (“crust” of the earth) is not a single rigid cover, but many interlocking puzzle pieces called crustal plates A crustal plate is a large piece of continental or oceanic crust that floats and slowly moves on top of the asthenosphere Convection currents cause movement of these plates Hot material of the mantle create currents that move a few centimeters a year

Plate Tectonics The theory of convection currents causing crustal motion, is called Plate Tectonics. Theory that the lithosphere consists of crustal plates that slowly move across Earth’s mantle and interact at their boundaries

Plate Interactions: Types of Interactions Crustal plates interact at their boundaries which supports the theory of plate tectonics. These different types of boundaries result in events such as volcanic eruptions, earthquakes, and rising of mountains

Three general classes of boundaries: Convergent- two plates pushing together Divergent- two plates moving apart Transform- two plates slide against each other

Convergent Boundaries Because the plates come together one plate will dip under the other into the mantle, causing the solid material to melt (this is a cause of volcanic activity) Plates may also “crash” head-on into one another, resulting in very strong earthquake or the raising of new mountain ranges

Divergent Boundaries As the two plates move away from each other magma from the mantle rises into the crack and cool to form new rock. These boundaries are responsible for driving the motion of other plates. Plates are like a conveyer belt, as they move away from the divergent boundary, they move towards the convergent boundary.

Transform Boundaries San Andreas Fault Since the plates rub against each other crustal matter, is neither created or destroyed as with the other types of boundaries Earthquakes are very common at these boundaries. The friction of the plates moving beside each other physically causes the motion of all the solid material in the crust.

Plate Tectonics and Sea Floor Spreading Sea floor spreading occurs when crustal plates separate at mid-ocean ridges the youngest rock is located closest to the spreading centre, b/c the fresh magma that rises to the surface cools to becomes rock

Plate Tectonics and Sea Floor Spreading Sea floor spreading occurs when crustal plates separate at mid-ocean ridges Older rocks are found further from the center, as they are constantly replaced by the new rock form by cooling magma. This has been verified by deep-sea drilling operations

More evidence for sea-floor spreading and plate tectonics is proven by paleomagnetism The study of the magnetic properties of rock in a past geological era.

parts of the sea floor have rocks with magnetic fields pointing in opposite directions when new rock is added to the edge of the dividing plates, it records the current orientation of the Earth’s magnetic field. we can see from this that the Earth’s magnetic field has reversed more than once.

Assignment Complete Q’s 1-3, 6 & 7 (pg 301) Webquest 1 – Traveling to Middle Earth

C 1.2 & 1.3- Early Life

Geological Eras Geological eras are sections of the Earth’s geological history, divided up according to major events such as mass extinctions and geological catastrophes There are four major geological eras: Precambrian Paleozoic Mesozoic Cenozoic Each era is broken down into smaller divisions called periods. In some cases, periods are broken down into epochs.

They are determined by major environmental or geological change. Era: They are determined by major environmental or geological change. Fossil records are mainly used to determine an era

Period: Periods are based on recognizable crustal changes that occurred in one or more areas. Some recognizable crustal changes used are the formation of mountain ranges or the collision of tectonic plates.

Epochs: They are established upon the rise and fall of the sea levels around the world. Epochs are only recognized in the Cenozoic era, this is due to erosion.