Jigsaw Fit:
Jigsaw fit refers to the phenomenon where two landmasses on opposite sides of an ocean appear to fit together like puzzle pieces. This concept is often used to describe the similarities between the East and West coasts of the Atlantic Ocean. The idea is that these similarities suggest a potential connection or shared geological history between these regions.

Similarities on the East and West Coasts of the Atlantic Ocean:
1. Mountain Ranges: Both the East and West coasts of the Atlantic Ocean have mountain ranges that run parallel to the coastline. For example, the Appalachian Mountains in North America and the Caledonian Mountains in Europe have similar geological origins.

2. Rock Types: The rock types found on both coasts are comparable. This includes similar types of sedimentary, metamorphic, and igneous rocks, indicating similar geological processes in both regions.

3. Fossils: Fossils of similar species have been discovered on both the East and West coasts. For instance, the same types of marine fossils have been found in sedimentary rocks in both North America and Europe.

4. Geological Structures: There are various geological structures found on both coasts that show similarities. This includes faults, folds, and other features that suggest a shared tectonic history.

5. Continental Shelf: The continental shelf, the shallow underwater extension of the continents, shows similarities in depth and width on both coasts. This indicates a common geological history and suggests that these continents were once connected.

Implications:
The similarities found on the East and West coasts of the Atlantic Ocean suggest several important implications:

1. Continental Drift: These similarities support the theory of continental drift, which states that the Earth's continents were once connected and have since drifted apart. The jigsaw fit observed between the East and West coasts of the Atlantic Ocean provides evidence for this theory.

2. Pangaea: The similarities between the East and West coasts suggest that these landmasses were once part of the supercontinent Pangaea. As Pangaea broke apart, the continents moved away from each other, creating the Atlantic Ocean.

3. Plate Tectonics: The similarities also indicate that both the East and West coasts of the Atlantic Ocean are located on the same tectonic plate, known as the North American and Eurasian plates. This suggests ongoing geological processes and potential future changes in the region.

In conclusion, the jigsaw fit observed between the East and West coasts of the Atlantic Ocean, including similarities in mountain ranges, rock types, fossils, geological structures, and the continental shelf, provide evidence for continental drift and the historical connection between these regions. These similarities support the theory of plate tectonics and the existence of the supercontinent Pangaea.