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PHYSICAL GEOGRAPHY:An overview

Prof. Anthony Grande

©AFG 0913

TOPOGRAPHIC RELIEF

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Definitions

Geography: Study of people living on the surface of the earth.

Geology: the study of the earth and its processesGeology: the study of the earth and its processes.

Geomorphology: the study of landforms.

Topography: the study of surface features.

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GEOLOGIC PROCESSES

TECTONIC (building)

Folding

Faulting

Volcanism

GRADATIONAL(wearing down)

Weathering: mechanical and chemical (in place)

M ti

NATURAL PROCESSESMass movements

Earthquakes

Volcanic eruptions

Subsidence

Mass wasting (by gravity)

Agents of Erosion (with movement: take-move-place)

- Running water

- Moving ice

- Wind

- Wave action

- Long shore currents 4

Folding

Folded rock layer in the Catskills.

Forces at work: Compression, bending, breaking 5

Faulting

Lake Champlain, Lake George and Sacandaga Lake are in rift valleys (also called grabens).

Forces at work: movement, tension, breaking 6

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New England Seismic Networkincluding NYS

Earthquakes occur throughout NE United States and SE Canada.

- Two major clusters in t NYeastern NY.

- One minor cluster in western NY.

Earthquakes are caused by adjustments to the earth’s surface (rebound)

as tension is released.7

Zones of Seismic Activity in NYS

1. LAURENTIAN ZONE

3. CLARENDON-

Source: NYS Museum

LINDEN ZONE

2. RAMAPO ZONE

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NE US Earthquake Hazard Zones

1least

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greatest

Volcanism

Forces at work: melting, movement of molten material, explosive 10

Types of Rocks

There are 3 categories of rocks, each formed differently, each with different resistancesdifferent resistances to erosion:Sedimentary

Igneous

Metamorphic Watkins Glen State Park,Tompkins Co.

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Types of Rocks

• Sedimentary – Rocks formed by the compaction of eroded material from other rocks or precipitates from dissolved minerals under pressure from the weight of successive layers.

They make up 75% of the earth’s surface.

Watkins Glen State Park,Tompkins Co.

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Sedimentary Rocks

Sediments are laid down in horizontal layers.

The layers are then often d f d b f ldi ddeformed by folding and faulting or displaced by volcanic activity.

They are eroded by running water.

in Ausable Chasm, Essex Co.

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Helderberg Escarpment

Hudson Valley Lowland

Catskills

Cliff face

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Types of Rocks

• Igneous – Rocks formed by the cooling and solidification of molten material.

The rate of cooling determines its crystallineThe rate of cooling determines its crystalline structure.

The rate of cooling determines the creation of minerals.

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Igneous RocksIgneous rocks are found at the surface in:

(1) SE NYS from Staten Island to Rockland Co. along the Palisades sill.

(2) NE NYS in the Saratoga Springs area where there are hot springs and pillow lava formations. (Pillow lava is a formation created when molten rock hits cool water.)

(3) The Hudson Highlands and Adirondacks contain Pre-Cambrian igneous rock.

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Palisades Sill

Sill: a horizontal underground lava flow intruded between layers of sedimentary rock.

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Igneous Rocks

Pillow lava at Stark’s Knob, NY >>

Below, recent pillow lava underwater off of Hawaii.

<<Volcanic sill, Haverstraw, NY (Rockland Co.) related to the Palisades formation. 18

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Types of Rocks

• Metamorphic – Rocks formed by the addition of great heat and pressure to existing sedimentary, igneous and metamorphic rocksmetamorphic rocks.For example,

shale (sed.) becomes slate

sandstone (sed.) becomes quartzite

limestone (sed.) becomes marble

granite (ign.) becomes gneiss

basalt (ign.) becomes schist.

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Metamorphic Rocks

Metamorphic rocks are found in eastern NYS (Taconic Mts., Hudson Highlands and the Manhat-tan Prong), the Adirondack Mts. and in the Thousand Island region (Frontenac Arch)

Adirondacks

Frontenac Arch (Thousand Is)

Taconic MtsIsland region (Frontenac Arch). Taconic Mts.

Hudson Highlands

Manhattan Prong

Banded gneiss in Adirondacks. 20

Resistance of Rocks

The composition of the rocks give them the ability to resist forces of erosion. Igneous and metamorphic rocks are generally

stronger. They are resistant to erosion and form highlands.

Sedimentary rocks tend to be weaker. They are found in lowlands.

Together they give us a variety of surface features and slope angles.

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Setting of Niagara Falls

The Niagara River drains Lake Erie.

It flows over the Ni E

GORGE

Lake Erie 22 miles upstream of the Falls.

Moved 7 miles in 12,000 yrs

Niagara Escarp-ment to reach Lake Ontario.

In doing so for 12,000 yrs, it has created a 7 mile long gorge as the falling water eroded weak layers of rock.

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9 miles from escarpment16 miles from the Falls

Niagara Escarpment

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Retreat ofNiagara

Falls

At the present rate of erosion it will take thewill take the Niagara River 75,000 years to reach Lake Erie.

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<< Each layer of rock has a different resistance to water erosion.

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Niagara Falls

American Falls

1969

2011

www.dailymail.co.uk/news/article-1338793/Niagara-Falls-ran-dry-Photos-moment-iconic-waterfall-came-standstilll.html - photos of dry Niagara Falls in 1969

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Niagara Falls

Horseshoe or Canadian Falls 26

Genesee River

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Letchworth State Park

Genesee River in the “Grand Canyon of the East.”

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High Falls on the Genesee River at

Rochester

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Present Geology of NYS

Generalized Geology Detailed Geology

THE GEOLOGY OF NYS IS VERY COMPLEX 30

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Detailed Geologic Map of NYS

Hot links to the fold out map that comes with the “Geology of New York State” book:

http://geology.about.com/library/bl/maps/n_statemap_NY3100.htm

http://geology.about.com/library/bl/maps/n_statemap_NYexplan.htm

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Bedrock Geology and Surface Landform Features of NYS

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Terrain Units

1. Mountains2. Plains3 Hills3. Hills4. Plateaus5. Coasts

NYS is unique in that all major landform units are found within its borders.

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Elevations within NYS

Elevations range from 0 ft (sea level) along the shores of Long Island

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of Long Island and the Hudson estuary to 5,344 ft at Mt. Marcy in the Adirondacks.

Landscape Characteristics

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Areas of Excessive Slope

36From Thompson, Geography of New York State

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Cross-sections

N

E

S

W

Appalachian Plateau

Tug Hill/Adirondacksg

S

W

N

E

Catskills

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Climate Regions of NYS

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System of Rivers and Lakes as part of the physical landscape

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Landscapes of NYS

• Land + climate provides the basis of lakes, rivers, soil and scenery. It is a finite resource, one that cannot be manufactured by people. >>PHYSICAL LANDSCAPE

• People manage it and reap its harvest: crops, forest products, wildlife and minerals.

• People tend to concentrate their settlement on the best lands: flat with fertile soil, ease of construction, fresh water supply and access to transportation routes. >>CULTURAL LANDSCAPE

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