Precambrian Super Eon
About a billion years ago, during the Precambrian Super Eon, our part of the world was much smaller than the present day continent of North America. Off the coast, to the east, were microcontinents of volcanic islands with intervening seas and sedimentary basins. A modern example might be Indonesia with its many volcanic islands.
The westward moving microcontinents collided with the mainland, one after the other. The repeated collisions thrust the volcanic and sedimentary rocks up and over the continental edge. The thrust sheets of the separate landmasses were pushed together, folded, buckled, invaded by magma, and pushed skyward to form the Grenville Mountain chain along the eastern coast of the continent. A modern example is the Himalayas formed by India colliding with Asia.
Under conditions of high temperature and pressure, volcanic and sedimentary rocks were transformed into metamorphic rocks. As the mountain chain eroded away over hundreds of millions of years, these rocks became exposed. They form the rolling hills west of Almonte we know geologically today as the Grenville Province of the Canadian Shield.