Scientists haven't created a geologic column in the sense of building one from scratch. Instead, they have constructed a conceptual model of the geologic column by studying rock layers across the globe.

Here's how it works:

1. Observing Rock Layers: Scientists observe the sequence of rock layers (strata) in different locations. They notice that these layers often have similar characteristics and contain similar fossils.

2. Correlation: By comparing rock layers from different locations, scientists can correlate them based on their characteristics and fossils. This process establishes a relative age for each layer, meaning they can determine which layer is older or younger than another.

3. The Geologic Time Scale: This correlation process has led to the development of the geologic time scale, which divides Earth's history into different eons, eras, periods, and epochs.

4. The Conceptual Model: The geologic column is a conceptual representation of this time scale, showing the different rock layers and their corresponding periods. It's important to note that no single location on Earth contains all the rock layers representing the entire history of Earth.

Therefore, the geologic column is a scientific construct based on observations and correlations across multiple locations, not a physical structure built in a lab.