What does the rock record tell us about New York's own deep past?
Use the Reference Tables Geologic History of New York State and the bedrock map to read New York's tectonic and environmental history, including ancient mountain-building, shallow seas and the most recent glaciation.
A Regents answer on New York's geologic history: how to read the Geologic History of New York State chart and the bedrock map together, the ancient mountain-building (orogenies), the shallow seas that left marine fossils and sedimentary rock, the oldest Precambrian rock of the Adirondacks, and the last ice age that shaped today's landscape, with worked exam questions.
Reviewed by: AI editorial process; not yet individually human-reviewed
Have a quick question? Jump to the Q&A page
Jump to a section
What this topic is asking
The Regents wants you to read New York's own geologic history from the Reference Tables Geologic History of New York State chart and the bedrock map: the ancient mountain-building, the shallow seas that left marine fossils, the oldest Precambrian rock of the Adirondacks, and the most recent glaciation. This pulls together relative dating, fossils, the time scale and the New York maps.
Reading the two New York references together
Shallow seas and marine fossils
Across much of the Paleozoic, New York lay near or below sea level and was repeatedly flooded by shallow seas. These seas deposited thick marine sedimentary rock (limestone, shale, sandstone) and preserved abundant marine fossils, corals, brachiopods, trilobites and crinoids, now found across the state. This is direct evidence that today's dry land was, at times, a shallow sea floor (and, combined with the uplift evidence, that the crust later rose).
Mountain-building (orogenies)
The Adirondacks expose some of New York's oldest (Precambrian) bedrock, uplifted metamorphic and igneous rock more than a billion years old; the bedrock map shows this old core surrounded by younger rock.
The last ice age
Most recently, during the Pleistocene ice age, continental glaciers advanced over all of New York. They left unmistakable evidence, which the surface-processes unit catalogues:
- Striated and grooved bedrock and broad U-shaped valleys (the Finger Lakes were deepened by ice).
- Unsorted till, erratic boulders carried far from their source, and moraines (ridges of dumped till).
- Reorganized drainage and many lakes and wetlands.
So New York's present landscape is largely a glacial landscape, shaped within the last couple of million years on top of a much older rock record.
Try this
Q1. State where the oldest bedrock in New York State is generally found. [1 point]
- Cue. The Adirondack region (Precambrian rock over a billion years old).
Q2. Explain what the wide presence of marine fossils across New York tells us about its past. [2 points]
- Cue. New York was repeatedly covered by shallow seas, which deposited marine sedimentary rock and preserved the fossils.
Exam-style practice questions
Practice questions written in the style of NYSED exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Regents (style)1 marksPart A. Marine sedimentary rocks containing fossils of corals and brachiopods are widespread across much of New York State. This is evidence that during parts of the geologic past, New York was (1) a high mountain range (2) covered by shallow seas (3) a desert (4) covered by thick ice. Justify your choice.Show worked answer →
A 1-point multiple-choice question. The answer is (2).
Corals and brachiopods are shallow-water marine organisms, and marine sedimentary rock forms on a sea floor, so their wide presence shows New York was repeatedly covered by shallow seas. A mountain range (1) erodes rather than forming marine rock; a desert (3) and thick ice (4) do not produce shallow-marine fossils. The trap is forgetting that today's land was, at times in the past, a shallow sea.
Regents (style)3 marksPart C. (a) Using the bedrock map, state where the oldest bedrock in New York State is generally found. (b) Explain what evidence shows that glaciers once covered New York. (c) Explain how the Geologic History chart records that New York experienced episodes of mountain-building.Show worked answer →
A 3-point extended-response question.
(a) 1 point: the oldest bedrock (Precambrian) is found in the Adirondack region (and in parts of the Hudson Highlands and New York City area).
(b) 1 point: glacial evidence such as striated and grooved bedrock, U-shaped valleys (the Finger Lakes), unsorted till, erratic boulders and moraines shows glaciers once covered the state.
(c) 1 point: the Geologic History chart lists mountain-building events (orogenies) and the rock and unconformities they produced, recording times when colliding crust raised mountains in or near New York.
Markers reward the Adirondacks for oldest rock, valid glacial evidence, and reading mountain-building (orogeny) events from the chart.
Related dot points
- Apply the principles of relative dating (superposition, original horizontality, cross-cutting relationships, inclusions and unconformities) to order events in a sequence of rock layers.
A Regents answer on relative dating: the law of superposition, original horizontality, cross-cutting relationships, inclusions, and how unconformities record missing time, used to put events in order in a cross-section, plus how faults, intrusions and contact metamorphism fit the sequence, with worked exam questions.
- Explain radioactive decay and half-life and use the Reference Tables Radioactive Decay Data to calculate the absolute age of a sample from the ratio of remaining radioactive isotope to its decay product.
A Regents answer on radioactive dating: what radioactive decay and half-life mean, the Reference Tables Radioactive Decay Data (Carbon-14 half-life 5700 years, Uranium-238 4.5 billion years), how to count half-lives from the ratio of parent to daughter, why Carbon-14 dates recent material and Uranium-238 dates ancient rock, with worked half-life calculations.
- Explain how fossils form, what index fossils are, and how fossils are used to correlate rock layers between distant locations and to infer past environments, using the Reference Tables.
A Regents answer on fossils and correlation: how fossils form, the features of a good index fossil (widespread, short-lived, easily recognized), how index fossils and matching rock match (correlate) layers between distant outcrops, what fossils reveal about past environments and evolution, and how to read the Geologic History of New York State chart, with worked exam questions.
- Describe how the geologic time scale is divided (eons, eras, periods, epochs), how its boundaries mark major changes in life, and use the Reference Tables geologic time scale to read ages and events.
A Regents answer on the geologic time scale: the divisions (eons, eras, periods, epochs), Precambrian time and the Paleozoic, Mesozoic and Cenozoic eras, how mass extinctions mark era boundaries, Earth's age of about 4.6 billion years, and how to read ages and events off the Reference Tables Geologic History of New York State chart, with worked exam questions.
- Explain how landscapes are classified (mountains, plateaus, plains) by elevation, relief and structure, how climate and bedrock control landscape development, and use the Reference Tables map of New York's landscape regions.
A Regents answer on landscapes: how mountains, plateaus and plains are classified by elevation, relief and rock structure, how climate (arid versus humid) and bedrock resistance shape landscape development, stream drainage patterns, and how to use the Reference Tables Generalized Landscape Regions and Bedrock Geology maps of New York, with worked exam questions.
Sources & how we know this
- Reference Tables for Physical Setting/Earth Science (2011 edition) — New York State Education Department (2011)
- Regents Examination in Physical Setting/Earth Science — New York State Education Department (2026)