Layers of the Earth Subtitle

The Earth is Made up of Three Layers ▪ The Core ▪ The Mantle ▪ The Crust

The Core-The Center ▪ The core makes up 31% of the total mass of Earth ▪ The Core is made up of mostly Iron metal. ▪ The inner layer of the core is solid ▪ The outer layer of the core is liquid. Inner Core Outer Core

The Mantle- The Middle ▪ The Mantle is the biggest portion of the Earth ▪ It is 68% of the Earth’s mass ▪ The mantle is rock, BUT it is extremely soft, very hot, and it moves! ▪ The two outer layers of the mantle play an important role in plate tectonics. Mantle

The Mantle- It’s Outer Layers ▪ Lithosphere is made of both the upper mantle and the crust. ▪ Broken into 15 tectonic plates ▪ Layer is solid and strong ▪ Asthenosphere is found below the lithosphere. ▪ Rocks are partially molten meaning they behave like a liquid. ▪ This “liquid” is what the Earth’s crust floats on top of. ▪ Layer is flexible, it behaves almost like silly putty. How the Mantle Moves the Plates

The Crust- The Outside ▪ The crust is the thinnest portion of the Earth representing 1% of it’s mass ▪ If the Earth was an avocado the crust would be the skin of the avocado. ▪ It is made up of solid rocks and minerals ▪ Contains all life on the planet ▪ There are 2 types of crust: ▪ oceanic ▪ continental Crust

Oceanic vs Continental Oceanic ▪ Oldest Oceanic Rock is 200 million years old ▪ Density of this rock is 3.0 g/cm 3 ▪ 3 – 8 miles thick ▪ Made of Basalt Rock Continental ▪ Oldest Continental Rock is 4 billion years old ▪ Density of this rock is 2.7 g/cm 3 ▪ Can be up to 22 miles thick ▪ Made mostly of Granite

Dating Oceanic & Continental Rocks ▪ Why do you think that oceanic rocks are so much younger than continental rocks? (look at the image below, what is happening to the oceanic crust?)

Finding the Age of Ancient Things ▪ Logically we can see now that because Oceanic Crust is more dense than Continental Crust AND because Oceanic Crust is re-absorbed into the Mantle at Subduction Zones between plates, it makes sense that Oceanic Crust is younger than Continental Crust…. ▪ BUT, How can scientists possibly know the actual ages of these plates?!?

Radioactive Dating Radioactive Dating uses Radioisotopes to determine ages ▪ Radioisotopes have nuclei that are unstable ▪ Unstable nuclei naturally lose energy and protons allowing them to decay into a more stable element ▪ The is called radioactive decay

Radioactive Decay ▪ Radioisotopes decay at a constant rate, no matter the temperature or pressure ▪ The rate at which radioisotopes decay is called its half-life ▪ The length of time that it takes for half of the parent isotope to decay into the daughter isotope ▪ Age is determined by measuring the ratio of parent isotope to daughter isotope

Which radioisotope to use? ▪ Different radioisotopes have different half lives ▪ Scientist use radioisotopes with longer half lives to date older rocks ▪ Uranium -235 is used to date older rocks like those at the bottom of the Grand Canyon ▪ Carbon-14 is used to date younger rocks such as those at the top of the Grand Canyon

Oceanic & Continental Rock Ages ▪ Oldest oceanic rock is 200 million years old ▪ Oldest continental rock is 4 billion years old