Edges of Earth's Crust Collided Here

Edges of Earth's Crust Collided Here. ... in the Patapsco Heritage Area. The rock looming in this cut here on the #9 Trolley Trial was once liquid magma that squeezed into a fault between pieces of the Earth's crust, then cooled to form Ellicott City granite. In the mighty construction project of 1898, workers rerouted the stream of Coopers' Branch, named for the coopers who made barrels in the area, to make room for the trolley tracks. Using hand tools and dynamite, they blasted through the rock to build Trolley Line #9 from Catsonsville to Ellicott City. Look for the hand-drilled holes the workers made in the rock to place dynamite for blasting., Ellicott City granite, technically, porphryritic gneiss, was a popular building material used in many structures in Ellicott City, Oella, and the region. For over a century, until the early 1900s, qurrymen mined the granite from such sites as Gaither's Quarry, Weber's Quarry, at right, and the site of the parking lot here at the foot of the Trolley Trail., About 500 to 445 millions years ago, two tectonic plates collided. One was the continental shelf edge of the North American plate, mud and sand deposits in shallow ocean water, and the other was the oceanic crust and volcanic islands similar to Japan today, called an island arc. In that collision, Ellicott City granite intruded along the irregular line of the boundary, as shown on the geological map at right. Waterfalls and rapids formed in the rivers and streams as they crossed from hard rock to the softer sand and clay of the Coastal Plain. This transition, called the fall line, extends from New Jersey to Alabama. Because ships could not navigate upriver beyond these falls and rapids, the major cities of the East Coast, Richmond, Washington, Baltimore, Wilmington, Philadelphia, Trenton, New York, developed as final destination ports on this line. The Patapsco River crosses the fall line downstream at Relay and Elkridge., In the 1700s, industrialists like the Ellicott brothers came to the Patapsco River Valley to use the tremendous power of its rivers and falls for milling grain, textiles, lumber, paper and other products., [Captions:] , Weber's Quarry, around 1898, now the site of the convenience store nearby on Frederick Road, inset below. The men on the face of the cliff operating the dragline, which extends down from the post on the right, are extracting granitic rock formed 15 miles below the surface and extremely rare east of the Appalachians and south of Nova Scotia., The nation's first cathedral, the early 1800s Baltimore Basilica, was built of Ellicott City granite., The Thomas Viaduct, spanning the Patapsco River in Elkridge, was built of Ellicott City granite and completed in 1835. The first multiple arch stone viaduct built on a curve, it is one of the oldest curved stone bridges still in use.