Hi Avicus
These are my first thoughts of your experiences....
The first time you meditated what I believe you experienced was the opening of the 'third eye' or 'eye of wisdom, which is known as the doorway to higher wisdom and intuition. Some psychic games for development are actually looking at a room then closing the eyes and remembering every bit of detail about the room and its contents. ie., count the doors and windows and see the walls and furniture in the room. Most people without trying, imagine that they are in the room. And they act as if they're in the room......if a person is watched while he remembers with eyes closed, his eyelids will probably be seen to flicker and his eyes may seem to move beneath the lids.
Some people are able to call up a memory image of a page in a book and read off, word for word what is written on the page. Others may see where the page is in the book but unable to read the words. Now that's a challenge!
Your second time meditating although alarming, sounds like you made (or almost made) a connection to the earth's pulsating energy. We don't see this energy in our waking state because it is so subtle. Again many train or practice to do this! Those that have seen it (the earth's energy) say it consists of spirals and little dots and webs of lines, sparks and clouds, an intricate network of energies all blending magically together to create a powerful living circuit. (We spin connectors between ourselves and others too) This is invaluable source of healing energy and power.
Does any of this make sense to you?