Geology vs. Topography - State of Connecticut by Jen Piatek

One way to explore the relationship of geology and topography. The different colors represent different rock units, while the lightness/darkness of each color is due to elevation. Black lines represent faults.

Geologic information from the state geologic map , elevation information from the state LiDAR survey. LiDAR was resampled to 80 ft/pixel before uploading (each pixel represents an area of 80 x 80 ft).

The oldest rocks in the state are located in the upper northwest corner (cyan and green) and are metamorphosed sedimentary and igneous rocks of the proto-North American terrane (450-1,100 million years old). Lavender units in the east and southeast edge are metamorphosed rocks (mostly granitic gneisses) from the Avalon continental terrane (some 600-700 million years old, others 370 myo). Yellow units in both the east and west, and green units in the eastern part of the state were originally part of the seafloor beneath the Iapetus ocean and were metamorphosed during the continental collision that closed that ocean basin (350-500 million years ago). Finally, brown units in the central basin are sedimentary rocks deposited during Mesozoic rifting (late Triassic/early Jurassic) - these are interspersed with basalt dikes and surface flows (red units) related to that rifting. Black lines identify the location of faults.

The geologic map units were grouped into terranes using information from the geologic map, downloaded in ArcGIS format from the CT DEEP (available from the GIS database www.ct.gov/dep/cwp/view.asp?a=2698&q=322898&depNav_GID=1707  - for an online version, see also mrdata.usgs.gov/geology/state/state.php?state=ct ). Yellow units in both the east and west, and green units in the eastern part of the state were originally part of the seafloor beneath the Iapetus ocean and were metamorphosed during the continental collision that closed that ocean basin (350-500 million years ago).

Image processing completed in ENVI 4.1: the geologic map was first exported to an RGB image, which was "resampled" using an HSV transform with the LiDAR image as a base. Faults in the original transformed image came out white, so black lines were added to the final image via an image editing application.

For more information on the LiDAR dataset, see the caption of gigapan.com/gigapans/93443 or gigapan.com/gigapans/93332