1. Plate Tectonics, The Rock Cycle and the Geologic History of Vermont (Rocks, Rocks, and more Rocks)

2. ROCKS: 1.Igneous Rocks Cool from Molten rock - magma Intrusive and extrusive 2.Sedimentary Rocks Little pieces of other rocks that have been eroded, transported and deposited elsewhere 3.Metamorphic Rocks Squished and folded rocks Can originate from sedimentary igneous or other metamorphics basalt granite sandstone Limestone slate schist

3. The Rock Cycle:

4. Generalized Geology of Vermont Most of the rocks we find in Vermont date to between 550 and 350 million years ago!

5. Vermont Has ‘em All Rock of Ages Quarry Barre, Vermont Granite (igneous-intrusive)

6. Vermont Has ‘em All Marble (metamorphic) Lessor’s Quarry South Hero, Vermont Limestone (sedimentary)

7. Vermont Has ‘em All Slate (metamorphic) Eureka Slate Quarry Poultney, Vermont

8. Vermont Has ‘em All Marble (metamorphic) Vermont Marble Museum Proctor, Vermont

9. Vermont Has ‘em All Mt. Mansfield Schist (metamorphic)

10. Why are all these different rock types found in VT??? Igneous silurian-devonian Metamorphic silurian-devonian sedimentary Ordovician Metamorphic Cambrian Metamorphic Pre-Cambrian

11. The Rock Cycle and Plate Tectonics:

12. “Vermont” in the Pre-Cambrian: Grenville Super Continent (~1 billion years ago) No continents as we know them VT and New England didn’t exist yet One big landmass Landmasses have come together and Spread apart several times in Earth’s 4.5 billion year history

13. Cambrian Rifting ~550 mya - Iapetus Ocean Rifting to seafloor spreading Erosion and deposition of Continental shelf rocks (limestones, sandstones) Offshore deposition (shales and mudstones) Taconic Orogeny ~450 mya - convergence Offshore sediments Metamorhposed and thrust Over cambrian sedimentary rocks In the champlain valley Acadian Orogeny ~400-350 mya Continued convergence Emplacement of granite intrusions Then 350 million years of erosion Leaves us with the Vermont of today

14. So….what is it?

15. Questions to ask yourself Can you tell which of the three types of rocks it is? Can you see individual grains or crystals? If so, are they interlocking, or do they look like little pieces of rock? Are the minerals light colored or dark colored? Can you see “sheets” or foliations in the rock? Can you see folds or other structures? Does the rock react (fizz) with acid (HCl)?

16. Basic Rock Type

17. Minerals - Igneous Rocks Felsic Minerals: rich in Si and O generally lighter in color less dense than mafics Mafic Minerals: rich in Fe and Mg generally darker in color more dense than felsics CoarseFine Cooling rate Intrusive Extrusive

18. Igneous Rocks

19. Sedimentary Rocks Detrital = Clastic HCl fizz Organic Chemically precipitated

20. Metamorphic Rocks

21. Metamorphic Rocks - precursors or parent rocks: Metamorphic RockParent Rock Quartzite Marble HCl fizz slate sandstone Limestone shale