Sociologists: What kind of sampling method is it when you make an open survey that anyone can answer?

Qualitative cross-sectional, maybe?

It’s cross-sectional if you’re only surveying them once. If you do it again at a later point in time, it’d be longitudinal.
Your method of collecting data is a self-administered survey, meaning people fill out a already complete survey with the same questions for everyone and they answer the questions independently (as opposed to someone interviewing them).
You have to think about whether it’s deductive or inductive. Does it use a generalization to explain/reason specific cases, or does it utilize specific instances to make a broad generalization about something that happens? General -> specific = deductive. Specific -> general = inductive. In other words, deductive is when you have a theory and you look for it in the world. Inductive is when you observe behavior and create a theory.

Sample of convenience.

@wundayatta Why did you bothering answering my question?

@Allie and @bkcunningham Thank you for giving real answers, especially @Allie for the thorough explanation.

@BringsTheNight Because that’s what it is. It is the correct answer.

Agree with @wundayatta. Since it is open to anyone, it is unlikely to be cross-sectional, since respondents would all need to have a common characteristic.

My apologies. I stand corrected. Good answer, @wundayatta.

@BringsTheNight I appreciate the apology. We’re good now.