Geologic Time - Rock Types

Geology

Geology Summary

This simplified geology chart summarizes the eras, periods, and epochs of geologic time. Included is a chart of the 4 main types of rock.

Geologic Time Chart . . Four Main Types of Rocks . . Mohs Hardness Scale

Geologic Time Summary
Era	Period		Epoch	Conditions	Duration (millions years)	Years Since (millions of years)		Evolution of Life Animals . . . . . . Plants
							0
Cenozoic (1st) (65M)	Quarternary		7. Holocene		10K	10K		Man
						0.5
			6. Pleistocene	icy	2	0 - 2
							2
	Tertiary	Neogene (25M)	5. Pliocene	cooler, dryer	11	2 - 13		Mammals increase
			4. Miocene		12	13 - 25		Grazing animals	Grasses
			3. Oligocene		11	25 - 36		Saber-toothed cats
		Paleogene (40M)	2. Eocene		22	36 - 58		Horses
		Paleogene (40M)	1. Paleocene		7	58 - 65		Birds, mammals	Flowering plants
							65
Mesozoic (2nd) (160M)	3. Cretaceous				71	65 - 136		Dinosaurs dissappear
	2. Jurassic				54	136 - 190		Dinosaurs rule	Conifers
	1. Triassic			volcanic	35	190 - 225		Dinosaurs appear
							225
Paleozoic (3rd) (375M)	6. Permian				55	225 - 280		Many reptiles
	5. Carboniferous				(65)
							280
		Pennsylvanian		warm, swampy	30	280 - 310		Reptiles
		Mississippian		land increase	35	310 - 345		Amphibians, insects
	4. Devonian				60	345 - 405		Fish
	3. Silurian				20	405 - 425		Air-breathing animals	Spore land plants
	2. Ordovician				75	425 - 500		Seaweed
	1. Cambrian				100	500 - 600		Marine Invertebrates
							600
Pre-cambrian	2. Proterozoic				900	600 - 1,500		Primitive invertebrates	Marine plants
	1. Archeozoic			granite, gneiss crust formed	2,500	1,500-4,000		One-celled organisms	Algae
							4,000
60	100	80	80	80	50	70	40	110	100
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The Four Main Types of Rocks
	Description	Examples
Igneous	Volcanic rock that is ejected from a volcano - fast cooling	lava, obsidian, pumice
Plutonic	Intrusive volcanic rock that is NOT ejected from a volcano - slow cooling	basalt, diorite, gabbro, granite
Sedimentary	Layered by accumulated sediments	breccia, chert, flint, limestone, shale
Metamorphic	Sedimentary or igneous rock transformed by intense heat and pressure	coal, gneiss, marble, schist, slate
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Mohs Hardness Scale
Mohs Scale	Absolute Hardness	Mineral	Examples
1	1	Talc
2	3	Gypsum	Fingernail
3	9	Calcite	Copper penny, gold, silver
4	21	Fluorite	Iron, platinum
5	48	Apatite	Steel - hard enough for gems
6	72	Feldspar (Orthoclase)	Glass, pyrite
7	100	Quartz	Scratches glass
8	200	Topaz	Emerald, aquamarine
9	400	Corundum, Saphire, Ruby	Twice as hard as topaz
10	1,500	Diamond	4 times as hard as corundum

DISCLAIMER

Although the author has tried to be as accurate as possible, errors are possible.

I could not find a simplified online geology table like the above. So, I made this geology chart, to help myself understand the relationships between the eras, periods, and epochs. I hope that it helps you.

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This Vaughns 1-Pagers Geology Summary web page was updated on 2006-04-30.