Liberty Enlightening the NY-NJ Harbor Estuary EarthCache
Liberty Enlightening the NY-NJ Harbor Estuary
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Waypoint 6 of 10 on Going Coastal’s NY-NJ Harbor Estuary EarthCache Discovery Trail in Liberty State Park, caches developed by Going Coastal, Inc. (www.goingcoastal.org) as a special project in affiliation with Groundspeak and support from the NY-NJ Harbor Estuary Program and the New England Interstate Water Pollution Control Commission.
The NY-NJ Harbor Estuary EarthCache Discovery Trail is meant to help visitors develop a better understanding of the Estuary, build environmental knowledge and foster stewardship.
The cache overlooks Upper New York Bay where you can view the natural and human developments of the New York-New Jersey Harbor Estuary. (visit link) From corner to corner, you are seeing an arm of the sea called an estuary. Estuaries are where rivers meet the sea, transition zones where salty seawater and fresh river water mix in a protected embayment.
The story of the NY-NJ Harbor Estuary starts some 125 million years ago with the rifting of Tectonic Plates causing the breakup of the great super-continent Pangaea. (visit link) The split formed the Atlantic Ocean when North America pulled apart from Europe. The Earth’s climate went through Ice Ages where it cooled then warmed called Glacial and Interglacial periods. The current ice age, called the Wisconsin glaciation began 2 million years ago. When the giant ice sheets slid across North America they stopped at about where you are standing, 40 degrees north latitude.
When the glacial ice sheet came down over this area, it was 1,000 feet high. It would have covered all but the very top of the 1,250-foot tall Empire State Building. During Jersey City’s formative years, glacial till deposit and glacial melt water created a marshy habitat on this shore.
The ice built a ridge of glacial debris (moraine) that blocked The Narrows and connected Brooklyn and Staten Island, called the Harbor Hill Moraine. (visit link) The glacier pushed rocks and dirt and deposited the debris when it began to thaw.
Think of a snowplow pushing everything in front of it.
The modern estuary took shape almost 18,000 years ago when the ice started to retreat. As the glacier melted, sea level rose in the Upper Bay. Eventually the water burst through The Narrows, opening the passage that is the “gateway” to New York Harbor and forming the present path of the Hudson River.
In prehistoric times, Liberty (Bedloe) and Ellis islands were small hills on the mainland. Now, less than 2,000 feet from where you stand, the Statue of Liberty welcomed over 12 million immigrants between 1892 and 1954 to the processing station on Ellis Island. Most of the immigrants’ boarded ferries for the Central Railroad of New Jersey Terminal (CRRNJ) to get to their new homes in America. Visitors can explore the historic CRRNJ Terminal at the northern end of Liberty State Park and board ferries that sail to the Statue of Liberty and Ellis Island Immigration Museum.
The Hudson is a 315-mile long river that flows southeast from its headwaters at Lake Tear of the Clouds in the Adirondack Mountains to meet the East River and form the Upper New York Bay. (visit link) The direction of the Hudson River’s flow is controlled by ocean tides. As the tide rises, ocean currents push north about 150 miles upstream in the Hudson River to Troy Dam. Low tides reverse these currents. The tides stop and reverse direction four times during a tidal day, which is 24 hours and 50 minutes. Because of this tidal flow, the river is said to “flow two ways.”
Tidal currents are the estuaries liquid transport for organisms, sediments, circulating and renewing nutrients and oxygen, and removing wastes. Tides are the up and down movements of water; the rise and fall triggered by the gravitational pull of the moon primarily, and much less by the sun. Tidal currents are the horizontal movement of the water. It is a flood tide current when the tide is rising and ebb tide current when the tide is falling. When the tide is at its highest or lowest point the current stops briefly before it reverses, this is called slack tide.
In addition to tides and currents, the Harbor Estuary has a very unique water circulation pattern called a salt wedge. A wedge-shaped layer of denser saltwater flows along the bottom, under the lighter fresh water floating on the surface. (visit link) This makes for a moderately stratified estuary; meaning salt water and fresh water are only partially mixed. You can tell how well the seawater and river water are mixing by measuring the salinity (level of salt) in the water. The estuary's salinity level varies depending on the season and weather, spring rains and snowmelt increase fresh water flow. The daily mixing leads to dynamic biochemical conditions in the estuary.
Now, see how clear the water looks. When there is a lot of dirt and sand floating in the water it makes the water turbid. This is from suspended sediments of eroding rocks and minerals transported by the Hudson River. The ocean tidal currents carry silt and clay. Murky water prevents sunlight from piercing the water depths, inhibiting photosynthesis and making it difficult for plants and animals to live here. The sediments will slowly settle to the sandy bottom of the bay.
In addition to salinity and turbidity, water quality relies on stable temperatures, dissolved oxygen, and pH. Water temperature and dissolved oxygen (DO) are critical factors for marine life. Dissolved oxygen is a byproduct of photosynthesis and wave circulation. pH is the measure of how acidic or alkaline the water is. Pure water has a neutral pH of 7.0. Marine organisms can stand a pH range of 6.5 and 9.0. Seawater provides a comfortable pH of 7.5. Measuring these dynamics can help understand how human activities and natural events impact the ecosystem.
Logging Activities:
1. Name a glacial feature visible on the horizon?
2. Look closely at the movement of the water. Can you tell what the tides and currents are doing? Is the current flowing up the river or coming down into the bay? Note date and time of your visit.
3. (Optional) Human activities and natural events continue to change this ecosystem. Name one human activity that changed this ecosystem. Name one action you can take to help improve estuary health.
4. (Optional) Take a picture with Lady Liberty in the background and post to your log.
To log a find on this earthcache, email the cache owner (DO NOT POST IN YOUR LOG), unless instructed otherwise. Use your GPS device to locate the next cache - GC2T1MP.
Remember, to upload a photo and let us know in your log ways we can improve the trail.
To reserve a field trip for your class, please contact the educators at the Nature Interpretive Center at (201) 915-3409. Geomate Jr. GPS units will be provided for your group for your high-tech exploration of the geology and ecology of Liberty State Park. Additional resources are available online at www.goingcoastal.org (visit link)
Data Sources:
• Estuaries Live - (visit link)
• Harbor Estuary Program - (visit link)
• NOAA - (visit link)
• U.S. EPA - (visit link)
Name and Type of Land
Liberty State Park
200 Morris Pesin Drive, Jersey City, NJ 07305
Phone: (201) 915-3440
(visit link)
OWNER: NJ Department of Environmental Protection
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