Paterson's Geology - A Step Back in Time

Geology: Forming & Fostering Paterson

 

The basaltic cliffs of the Great Falls are a highlight of Paterson's fascinating geologic history

VIP Terry McKenna

 

Geologically speaking, Paterson's past is a varied and exciting one. Lava flows, upheavals, even the break-up of the supercontinent Pangaea - these events are all part of this area's geologic pre-history. The Falls and other natural features in Paterson give us clues to parts of this story. As you walk over the Falls, through Upper Raceway Park, and around the Great Falls Historic District, you'll see some of these clues.

The Falls is in a river valley, but unlike other river valleys (such as that of the Colorado River, where the river eroded the Grand Canyon) the Paterson Great Falls was not eroded into its current form. Instead, the rocky structure that supports the Falls is virtually unchanged from the past 12,000 - 14,000 years that water has flowed over the rocky cliffs. The Passaic Falls consist of basalt which is a fairly hard rock. By comparison, the Grand Canyon consists largely of limestone and shale, with sandstone. Limestone and shale are much softer than basalt and so were far more subject to erosion.

When Paterson was established, the basalt and especially sandstone were among the raw material that made Paterson an ideal place to establish an industrial city. Other raw materials were abundant wood, iron ore (nearby) and water, with the Passaic River providing waterpower. While the SU.M. (Society for Establishing Useful Manufactures) establishing a manufacturing city beginning with the spinning of cotton, the quarrying of stone was also important. The earliest local quarrying was done at Mount Morris - now just a rocky outcrop at the edge of Overlook Park. This “mountain” was quarried to oblivion for its supply of sandstone (brownstone). The Morris Canal made quarrying in Little Falls possible, and quarried stone could be transported via barge to cities from Paterson to New York. If you look at the oldest houses and churches in the area, brownstone is the most common stone used in construction.

As railroads were established, the tracks required a gravel roadbed - the Watchung Ridge that touches Paterson was quarried for its harvest of basalt - traprock. Later on, traprock was used as aggregate in concrete, and by the 1920s it became the aggregate for asphalt roads (also known as blacktop). Traprock quarries followed the edge of the Watchung ridges, located along Valley Road in Clifton, in what is now Woodland Park, and in Little Falls where the newer sections of Montclair State University are located. Little Falls sandstone was used to build St. John’s Cathedral in downtown Paterson.

Garret Mountain and the Great Falls are part of a series of ridges known as the Watchung Mountains. These ridges were created by lava flows- a consequence of the breakup of Pangaea, the supercontinent that preceded the current arrangement of the earth’s land masses. In the case of the Paterson Falls, 225 million years ago the super continent of Pangea began to show signs of an eventual split. The portion that now contains Paterson (and eventually became the North American plate) began to sink as the earth’s crust spread apart and thinned to form a deep rift valley. As the land masses moved away from each other, hot magma found its way to the surface through existing faults. A marker at Mary Ellen Kramer Park commemorates the 50-mile long lava flow that includes the Falls. The flows occurred approximately 190 million years ago.

The Palisades were formed similarly. Instead of being of basalt, which is formed from lava (magma that comes to the surface), they are formed from diabase, a form of magma that intrudes close to but not all the way to the surface. Diabase and basalt are similar in that they have small or tiny crystals of their composite minerals. Other igneous rocks like granite are formed from magma that is much deeper (usually forming as ocean crust). Granite and other similar rocks cool more slowly and thus the crystals are larger.

If you look at the exposed rock, you will also see signs of the glaciers that covered northern New Jersey, including the area where Paterson is located.

- Text by Volunteer in Park Terry McKenna

 

Our planet is composed of layers of rock in solid & liquid form

NASA

A Kid's Introduction to Paterson Geology: Rocks, Water, & Time

What is "geology"?
Geology (from the Greek words "geo" for "earth" and "logy" meaning "study of") is the science of the physical features of the Earth and other planets and characterizes the various rocks and minerals. Geology is both a practical science used by industries and a theoretical science exploring how the Earth and other planets developed since forming. It helps predict earthquakes, plan and construct buildings and infrastructure like roads, dams, and bridges, and studies the ancient history of our and other planets. Geology teaches us how and why minerals, metals, oil, and other resources form where and when they do, and how the world may change in the future.

 

The rock cycle shows how the three types of rocks form and change.

USGS

The Rock Cycle
While they seem solid and permanent, rocks change over time. Some melt with great heat and pressure. Others are chipped and worn away through friction in processes known as "erosion" and "weathering." We call these changes the "rock cycle."

Like the water cycle, where water changes forms and location around the planet, the rock cycle helps map the ways rocks move and change into different types. Just as water can be a liquid, a solid (ice), or a gas (steam), rock can change form. Also, similar to how water evaporates into the sky, falls as rain, and flows in rivers and streams to oceans and lakes before seeping underground, rocks are pushed up from and back into the Earth's crust.

There are many types of rocks, but scientists sort them into three types: "igneous," "sedimentary," and "metamorphic." Each has different properties based upon how they were formed, and each can be transformed into another.


Igneous

• Under extreme heat rocks liquify - "magma" is molten rock underground, while "lava" is liquid rock that has broken through the planet's surface. Igneous rock is formed through the cooling and hardening of magma or lava. In other words, this is a volcanic rock, but it does not always have to come from a volcano. For example, when the supercontinent Pangea split apart (see below) cooled lava formed igneous rock.

Sedimentary

• Sedimentary rocks are made when sand, mud and pebbles get laid down in layers from either erosion or weathering. Over time, these layers are squished under more and more layers. Eventually, the layers are harden and turn to rock. Sedimentary rocks can be formed in deserts, lakes, rivers and seas.

Metamorphic

• A metamorphic rock is a type of rock which has been changed by extreme heat and pressure. The word metaphoric comes from two ancient Greek words:“meta,” meaning to change, and “morphe,” meaning to form.

Erosion

• Erosion happens when rocks and sediments are picked up and moved to another place by ice, water, wind or gravity (for example boulders falling into water and eroding into pebbles and sand).

Weathering

• Weathering is the process where rock is dissolved, worn away or broken down into smaller and smaller pieces. Unlike erosion, weathering happens without the rocks moving from place to place (for example, the side of a cliff).

 

Over millions of years the Pangean supercontinent split into the continents we know today

USGS

Pangea
Over 300 million years ago the seven modern continents were merged as one giant supercontinent known as "Pangea" (sometimes spelled "Pangaea"). This name comes from two Greek words: "Pan," meaning "all," and "Gaia/Gaea," meaning "Mother Earth."

Continental Drift & Plate Tectonics
The area where Paterson is today was located along a split between two massive continental plates. Continental and oceanic plates "float" on the Earth's molten outer core in a process called "plate tectonics". About 200 million years ago, Pangea began tearing apart as the North American and African plates pulled apart, causing lava flows. These hardened, forming the igneous basalt bedrock you see today at the Great Falls.

 

Expansion & contraction of Glacial Lake Passaic in Northern NJ between 25,000 & 14,000 years ago. The retreat of a massive glacier to the northeast allowed the huge body of water trapped by the mountains stretching southwest to flow from beyond Far Hills past Paterson and drain in four stages.

NJ DEP

Putting it Altogether – How Did the Great Falls Get Here?
Millions of years after the lava cooled, glaciers covered this region during the last Ice Age.

Glaciers
A glacier is a large area of thick ice that remains frozen from one year to the next. Like lava, glaciers flow slowly over the land. These periods, when huge portions of the Earth were covered in ice, are called a "glaciation." The Laurentide and Cordilleran ice sheets, first formed nearly 2.6 million years ago, expanded and contracted as the global climate cooled and warmed. These ice sheets were over 10,000 feet thick in some locations (nearly two miles in height).

The area around Paterson saw two major glaciers: the llinoian and Late Wisconsonian glaciations. The Illinoian glaciation formed about 150,000 years ago, while the Late Wisconsonian glaciation covered Paterson when it was at it's largest size, approximately 25,000 years ago.

These glaciers carved the landscape and formed the hills and valleys that make up the Watchung Range we see in the region today. They also rerouted the ancient path of the Passaic river. As the Late Wisconsonian glaciar melted, the resulting water formed a lake hundreds of feet deep known as Glacial Lake Passaic. This ancient lake was "proglacial," meaning it was formed by melting ice blocked from draining by the glacier itself.

Glacial Lake Passaic existed in Northern New Jersey up until about 14,000 years ago, when the glacier's retreat uncovered passes in the hilly landscape which allowed the prehistoric Passaic River to find a new route, draining Lake Passaic and carving a new path via the chasm of the Great Falls. The watershed of the Passiac River and its associated wetlands are the ancient remnants of this lake, forming the basis of the Great Swamp National Wildlife Refuge.

 

The National Park Service has a wide variety of geoscience resources

NPS

Learn more:

Check out these videos to learn more about the geology of Paterson and the Great Falls:
Geology Part 1 - How the Rocks Got to the Falls
Geology Part 2 - How the Passaic River Came to the Falls

Explore these links to learn more about geoscience and glaciers:
Geology in National Parks
Geoscience Concepts
Glaciers

Bring these concepts to the classroom with these teaching resource links:
Geoscience Teaching Resources
Glacier Teaching Resources

Visit the Paterson Museum to explore their mineral exhibit:
The Paterson Museum