Raiders of the Lost Ark wasn't interested in breaking new ground with narrative technique. It was a big, bold crowd-pleaser aimed at honoring smaller, older crowd-pleasers. Getting cute with the narrative by, say, following a nonlinear timeline or changing the point-of-view halfway through just wasn't in the playbook. Time moves forward in a linear fashion, no voice-over narration intrudes on the story, and there's not even a dream sequence to break it all up. What you see is pretty much what you get here.
Within that framework, however, Spielberg finds a few ways to tweak the traditional narrative formula. The first one comes in the opening scene, which is actually the climactic close to an entirely different story we don't get to see. Why does Indy want the idol in that Temple? What did he have to do to get the map? How did he join forces with those two creeps he's with? We never find out and we don't have to. All we get is the payoff. It's a great way to introduce us to this character and how he does things, all without lot of chunky exposition. (In fairness, Raiders borrowed the technique from the James Bond films, which had been doing it for years.)
The narrative also needs to conform to the specific beats of movie serials, which differ slightly from the traditional narrative formula of rising action that your English teacher keeps going on about. The serials were originally broken up into multiple parts and screened one per week. You would watch Chapter 6, all fifteen minutes of it, and have to come back next Saturday if you wanted to see Chapter 7.
The filmmakers usually sweetened the pot by leaving things on a cliffhanger: The hero's stuck in a burning house, for example, or the heroine is about to get cut in half by a buzz saw. That left a whole lot of "mini-climaxes" instead of the traditional slow rise in action. (Stop snickering!) The final episode might be particularly epic, but beyond that the tone was pretty uniform, with no variation.
Raiders has to copy that formula, but because it basically crams all those episodes into one feature-length extravaganza, it has to follow the traditional narrative arc as well. It's a surprisingly tall order, but it manages the task nicely. We get specified beats of action—like the fight at the bar in Nepal, the brawl on the streets of Cairo, Indy and Marion getting buried alive, etc.—that still progress toward a big finale.
Each stop feels a little bigger, each threat just a little more dire. First Indy's got to get by snakes, then a pair of mechanics, then a whole convoy of Nazi troops, then a Nazi sub… You get the idea. Spielberg paces them to capture the rhythm of the old serials while still following through on the needs of a more traditional narrative. Like we said earlier, this movie makes us think about explosions far more than we thought we would.