Learn German: Die Absperrung blockiert den Weg. - The barrier is blocking the path.

Weg is a masculine noun (der Weg). Because it is the direct object of the verb blockieren (the thing being blocked), it must be in the accusative case. For masculine nouns, the article der changes to den in the accusative.

Does German have a separate form for "is blocking" versus "blocks"?

No, German doesn't have a continuous tense like English does. The single present tense verb blockiert covers both "blocks" and "is blocking." You simply choose the one that makes the most sense in English context!

If I wanted to say "The barrier blocked the path" in the spoken past tense (Perfekt), would it be "hat geblockiert"?

No, it would be hat blockiert. Verbs that end in -ieren (like blockieren, studieren, passieren) are a special group. They do not take the ge- prefix when forming the past participle.

Are all nouns ending in -ung feminine like die Absperrung?

Yes! Whenever you see a noun ending in the suffix -ung, you can confidently use the feminine article die. These nouns are typically built from verbs, just like Absperrung is derived from the verb absperren (to cordon off).