Journey to the Surface of the Earth, part 1 Or, Earth from the Inside-Out September 13, 2018
The Earth’s Interior Today we will discuss these points: How we know about the interior of the Earth… How Earth’s interior took on the characteristics it has… The layers of the Earth as defined by composition Tomorrow we will discuss: The layers of the Earth as defined by behavior… September 13, 2018
The Differentiated Earth… Earth shows differentiation Separation into layers due (in this case) to differing densities Just like separation shown here September 13, 2018
How Do We Know About Earth’s Interior Three ways, actually! First, volcanic data brings some of the interior up to us. Second, density information… Since the overall density of the Earth is 5.5 g/cm3 and the density of the surface is 2.2 g/cm3, the interior must be denser! Third, seismic (earthquake) waves act like an “ultrasound” and give a picture of the interior September 13, 2018
How Do We Know About Earth’s Interior September 13, 2018
How Did Earth Become Differentiated? Earth became differentiated very early in its history (around 4.5 billion years ago) during the Great Bombardment As material from space hit the young Earth, the heat from the impact melted the Earth leading to a magma ocean September 13, 2018
Demo – How Earth Became Differentiated Describe the demonstration you just saw and heard. What position were the marbles in originally? What brought about the change? Where did the marbles end up? Why? September 13, 2018
The Iron Catastrophe The Iron Catastrophe is the name given to this event Heavy elements (iron, nickel) sink to the center of the Earth Lighter elements (silicon, oxygen) rise to the surface September 13, 2018
So, What’s the Big Deal? This early layering led to the way our planet functions today AND to the way life developed! Stay tuned for more on this tomorrow! September 13, 2018
Earth’s Layers Earth’s layers are defined two ways Layers defined by composition are the core, mantle, and the crust (oceanic and continental) Layers defined by “behavior” are the inner core, the outer core, lower mantle, asthenosphere, and lithosphere September 13, 2018
September 13, 2018
Layers Due to Composition Core Innermost layer of the Earth Composed of nickel and iron Metallic, not rocky like the other layers Very dense – more than 6x the density of the surface Makes up one-third of Earth’s mass and is 3480 km thick (of 6400 km total) September 13, 2018
Layers Due to Composition Mantle Middle layer of the Earth Rocky, rather than metallic like the core Composed of mafic minerals (silicates high in magnesium and iron (Fe) High quantities of peridotite Makes up 48% of the thickness and 67% of Earth’s mass September 13, 2018
Layers Due to Composition The Crust Outermost layer of the Earth Rocky, mostly silicates Two types Oceanic (most of the crust) – made of mafic rocks – mostly basalt Continental – made of felsic rocks – mostly granite September 13, 2018
Layers Due to Composition Oceanic crust is very thin Denser than continental rock. Continental crust is thicker – up to 75 km thick Question – since oceanic crust is denser, what happens when oceanic and continental crust interact? September 13, 2018
September 13, 2018
Summarize… What does differentiation mean? Why did Earth become differentiated? In what two ways are Earth’s differentiated layers defined? Identify one property each of the core, mantle, and crust. September 13, 2018