A Course in Rhode Island History #2: 1.1 RI Geography. Geology and Geographic Regions

Maybe it's the geography teacher in me, having taught it for five years back in the day. But knowing the answer to "where," so students understand the setting for the historical events, is to me as natural a starting place for survey course like this one as scenery and backdrop is to a theater's stage manager. 

This unit, while I think is interesting as all hell because of all the science, should only take a day or two at the beginning of the course. 

However, this is a foundational unit. The activities that will be associated with it, especially student-labeled maps of the state, are resources that students will return to over and over in the units that follow. 

Geology and Geographic Regions

Rhode Island's bedrock includes metamorphic, igneous and sedimentary rocks formed between the Precambrian to the Cretaceous period; in other words from before the time of the trilobites through the age of the dinosaurs. The state lies entirely on top of basement rock from the primeval microcontinent of Avalonia, which was created by an arc of volcanos along a subduction zone of the supercontinent Gondwana between .8 and .5 billion years ago. Avalonia includes coastal New England and Canada, southern Ireland and Britain and a sliver of northern Europe from France to Poland. Rhode Island today is also nearly at the exact geographic middle of the mountains that extend from southern Alabama to Newfoundland. The chunk of the Avalonia that contained Rhode Island became landlocked during the formation of the supercontinent of Pangaea and its rocks folded and deformed during the collisions that formed the Allegheny Mountains. This is also when the depression that became Narragansett Bay was formed. Once Pangaea broke apart Rhode Island was once again alongside a marine environment.

The terranes of Avalonia with modern borders for orientation: 1 Laurentia; 2 Baltica; 3 Proto-Tethys Ocean; 4 Western Avalonia; 5 Eastern Avalonia. US: United States; CT: Connecticut; MA: Massachusetts; NH: New Hampshire; ME: Maine; RI: Rhode-Island CA: Canada; NB: New Brunswick; NFL: Newfoundland; NS: Nova-Scotia; PE: Prince Edward Island Europe: IE: Ireland; UK: United Kingdom; FR: France; BE: Belgium; NL: Netherlands; DE: Germany; PL: Poland

The next major event to affect Rhode Island's topography was the Ice Age, when the Laurentide Ice Sheet covered much of North America. Rhode Island was covered by ice several times beginning 75,000 years BP (Before Present) with the ice finally retreating for the last time about 14,000 BP. Block Island was formed when as the glacier retreated and left a great pile of debris known as terminal moraine, at the furthest point the glacier reached. The south coastal regions of Westerly, Charlestown and Narragansett are referred to by geologists as the Charlestown moraine, from the same pile of glacial debris which includes Long Island and Fishers Island. Route One in South Kingstown and Charlestown follows the contours of this line of debris, as the highway was built just to the south of the moraine. The Charlestown moraine is most visible driving along Route One South from Wakefield to Haversham Corner in Westerly -- the steep hillsides to the right are the moraine.

Another feature -- glacial ponds known as kettle ponds -- were formed as the glacier melted. Chunks of ice embedded in the mud and till melted, some chunks more slowly than others. These slow meting pieces of glacier forming depressions known as kettles. Today these kettle ponds dot the landscape of Rhode Island, especially in South County. Watchaug Pond, one such kettle pond, is located just north of the Charlestown moraine, and it has a U.S. Fish & Wildlife Service Visitor Center and hiking trails replete with rocks left behind by the glacier.

Rhode Island largely consists of two geographic regions today. Southern and eastern Rhode Island consists of the coastal lowland, a continuation of the Atlantic Coastal Plain that extends from Florida to Cape Cod, and the Eastern New England Upland or "hill country," the western third of the state along the border with Connecticut. The lowlands were formed by glacial outwash and about 10% is windblown loess. Loess is extremely fine soil for agriculture. The soil in hill country in the western part of the state is glacial till (i.e., sediment deposited by a glacier), and is extremely rocky. These differences in soil resources will be important later in explaining the economic activities of both the Narragansetts and the English before the Industrial Revolution. 

Students should be able to infer from topographic maps that the best farmland is along the Bay and south coast, while Western RI might be better for hunting and gathering or harvesting lumber. They should also be able to draw on prior knowledge and/or personal experience that the landscape is crossed by numerous rivers, and they as well as the bay served as key transportation routes for both the Narragansett and the English. These alongside numerous Indian trails, where later roads and turnpikes were built over the trails, provided both the Narragansett and colonial-era English with the means to get from point A to point B. But when water power to drive textile mills became an important economic activity, the rugged hills in the north and west, with their rapidly flowing waters, will help drive the destiny of the state.

Reflecting on this part of Unit I, it will by design incorporate elements of the discipline known as Big History. Here is the Wikipedia intro blurb about it:

Big History is an academic discipline which examines history from the Big Bang to the present. Big History resists specialization, and searches for universal patterns or trends. It examines long time frames using a multidisciplinary approach based on combining numerous disciplines from science and the humanities, and explores human existence in the context of this bigger picture. It integrates studies of the cosmos, Earth, life, and humanity using empirical evidence to explore cause-and-effect relations, and is taught at universities and primary and secondary schools often using web-based interactive presentations.

While this course is not starting Rhode Island's history with the Big Bang, students should gain some sense of "deep time" from this unit, and understand that Rhode Island's landscape has not always been at all like it is now; Rhode Island has not occupied the same latitude or even been on the same continent. To imagine a kilometer of ice where we are living right now only a few thousand years ago, or what this place looked like as the first Paleoindians made their way into a world in transition. And that the landscape we know so well today is as ephemeral as that of the last dinosaur or first human to walk across this land we call Rhode Island.

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Image Credits:

Map 1. Rhode Island Topography Wall Map: http://www.outlookmaps.com/shop/rhode-island-topographic-map

Map 2. By File:AVALONIA.jpg, Public Domain, https://commons.wikimedia.org/w/index.php?curid=34366185

Map 3, Rhode Island Topographic Map: https://geology.com/state-map/maps/rhode-island-state-map.gif