"Learn more" Modal runs off of page; does not open in some cases

[lprivette]

Steps to reproduce:

1. go to https://nawqatrends.wim.usgs.gov/Decadal/
2. Click the "Learn more" button
3. another modal is either opened and runs off the screen OR is not opened at all.

On Dell laptop in Chrome, it opens but runs off screen.
On Dell laptop in Edge, it appears to open correctly.

On Hans' Surface in Chrome, modal did not open at all.