1. Understanding Maryland’s Geology Supplemental Diagrams Photo by Martin F. Schmidt, Jr.

2. ALWAYS!

3. My Story

4. Reasons to study geology Events of geologic history Underlying geology Land use by humans Landforms of an area is often controlled by are usually the result of was produced by So our decisions today can be affected by events that happened hundreds of millions of years ago!

5. Directions to study geology Events of geologic history Underlying geology Land use by humans Landforms of an area Science builds from data we can observe, and moves to making interpretations, so goes from top to bottom of this pyramid. But sometimes it's easier to understand if we look at the big picture of what has happened in the past, then see how this reflected in what we can observe.

6. Source: http://earth.rice.edu/mtpe/geo/geosphere/topics/2plate_tectonics.html How have the plates moved to create Maryland's geologic story?

7. Great Falls of the Potomac, NW of DCPhoto by Martin F. Schmidt, Jr. Best example of the result of the difference in erosion rates as streams flow from the Piedmont into the Coastal Plain:

8. For conclusions of Part B: How do structure and rock resistance interact to make the landforms of the provinces?

9. Winding Ridge What makes the high ridges in the Plateau? A resistant sandstone in the unit mapped here as the Pottsville Group makes a mountain each time the sandstone appears at the surface. Dashed lines shows where it has worn away. Cross-section from the Geologic Map of Maryland, 1968. Structure (folds) doesn’t always match the topography; here are anticlines that are valleys due to non-resistant rocks in the center of the fold.

10. How do structure and rock types interact in the Valley & Ridge? Sometimes the structure and the topography match. An anticline of resistant sandstone that makes a mountain. A syncline of non- resistant rock that makes a valley. Or they don’t match; here are 2 synclines with resistant rock in the center, so they make mountains. Sideling Hill is the syncline on the first slide of this PowerPoint. Cross-section from the Geologic Map of Maryland, 1968.

11. Resistant rock layers of the Valley and Ridge province. Originally from Maryland Geological Survey Bulletin 19.

12. How do structure and rock types interact in the Blue Ridge? The Blue Ridge is a large anticline with sub-folds (an anticlinorium). Where the very resistant quartzite of the Weverton Formation crops out on the surface, it makes the ridges of the Blue Ridge province: South Mtn. & Catoctin Mtn. The Catoctin Metabasalt show volcanoes & rifting occurred here when the supercontinent Rodinia broke up, and the Frederick Valley rift occurred when Pangaea broke up – about 400 million years later! Cross-section from the Geologic Map of Maryland, 1968.

13. Another way of seeing the complex folding in the Piedmont Complicated folding like this made the “dome” structures in the Baltimore area. The folded rocks are also folded in on themselves. Cross-section from the Geologic Map of Maryland, 1968.

14. For conclusions of Part C, section 3: As we look at the geologic structures across Maryland (west to east), what do they show about how the amount of forces varies?

15. The Appalachian Plateaus are underlain by sedimentary rock layers with broad, gentle, folds, sometimes described as “warped”; this contrasts with the tighter folds in the Ridge & Valley, as shown in this cross-section across most of the western part of the state. Sandstone layers then make the ridges in both provinces. Click for labels. Broad folds in Appalachian Plateau Tighter folds in Ridge & Valley Border between provinces AA’ B B’ C C’ DD’ E Cross-section from the Geologic Map of Maryland, 1968.

16. Piedmont. This is a cross-section of the rocks in the western Piedmont, showing many folds and faults (faults are the heavy lines with arrows on them). This is typical of the complex geology of the Piedmont. This complexity formed when the area which is now the Piedmont was a mountain range; what is left today is the geology at the roots of those mountains. Source: Union Bridge Quad Geologic Map, Jonathan Edwards, 1986.

17. Piedmont folds/nappe diagram; shows how deformed layers can be. Source: Phoenix Quad Geologic Map, Stuart Moller, 1979.

18. Blue Ridge: a large fold + metamorphosed. Valley & Ridge: tighter folds than Plateau. Plateau: broad folds = “warped.” Piedmont: complex folding & intrusions + metamorphosed. Coastal Plain: layers of sediment gently dipping toward the ocean. Added after continental collisions. Conclusion: continental collisions came from this direction. So from which side did the continental collision occur for Maryland? Which end of this car got hit? How can you tell?

19. A Wilson Cycle very much like the history of the Appalachians. Author: Lynn Fichter, James Madison University. Source: http://csmres.jmu.edu/geollab/Fichter /Wilson/Wilsnall.pdf More descriptions: http://csmres.jmu.edu/geollab/Fichter /Wilson/Wilson.html

20. The history of the Appalachians – and therefore Maryland - in one set of cross- sections. Source: Earth - Portrait of a Planet, by Stephen Marshak Precambrian: 1 Bya Ordovician: 450 mya Devonian: 375 mya Mississippian to Permian: 350-250 mya

21. Complete Maryland Geologic Cross-sections west of the Coastal Plain – Slide 1. Appalachian Plateau Valley & Ridge Border between provinces AA’ B B’ C C’ DD’ E Cross-section from the Geologic Map of Maryland, 1968.

22. Complete Maryland Geologic Cross-sections west of the Coastal Plain – Slide 2. Valley & Ridge Blue Ridge Piedmont Cross-section from the Geologic Map of Maryland, 1968.

23. Geologic Cross Section of the MD Coastal Plain, NW to SE Choptank & St Marys Cross-section from the Geologic Map of Maryland, 1968.