Maryland’s Environment: A 20,000
Year History of Change

Introduction

Over its 4.6 billion year history, the Earth’s crust has been shaped by intertwining chemical, physical, and biological processes. In the inexorable slowness of geologic time, the convection of the Earth’s mantle gave contour to the land. Tectonic movement and climatic cycles shaped ancient seas that created the unique foundation of the Middle Atlantic region of North America. Streams carved hills and valleys, and rainwater weathered rock into soil. At the time of their formation, Maryland’s mountains rivaled the Himalayas in size. Their rock slowly weathered, creating the softer contoured mountains we know today. Over time, Maryland’s bedrock became mantled by fertile soils, mineral deposits, and complex water features – which together create a habitable landscape that has long been attractive to human beings.

The political boundaries of the State of Maryland contain an ecologically diverse landscape. Its river systems feed the Chesapeake Bay, the Delaware River, and the Ohio River drainages, and an east-west span of 249 miles stretches from the Atlantic seaside to the Allegheny Plateau. Across the state, elevations climb from the ocean’s edge to 3,360 feet at Backbone Mountain in Garrett County. Granite bedrock protrudes from the surface of western Maryland, while a wedge of unconsolidated sediments blanket this rocky base to a depth of 8,000 feet at the Atlantic coastline. Maryland’s flora is similarly variable, being a product of the diverse soils, climate, and hydrology of the state.

Many different lines of evidence help us to understand how Maryland came to be as it is today. Accordingly, several disciplines contribute to our knowledge of Maryland’s environmental history. Specialists in geology, geography, climatology, archaeology, history, oceanography, paleobiology, zoology, botany, and marine studies help us explore the ways in which Maryland’s environment developed. One thing we have learned through their work is that the histories of Maryland’s landscape and of Maryland’s people are intertwined, and that each has influenced, affected, and shaped the other.

The following sections explore/investigate some questions surrounding key points in the development of Maryland’s environment over the past 20,000 years. A list of sources offers recommendations for further reading, and linked pages expand on some topics touched on in the text: