What an inconvenient place for this Pokemon to take a nap. Is there any room on either side of the road to go around it?

Nope. It is rather like a slow-flowing liquid, in that it has taken the shape of the road cut containing it.

Fiiine she'll turn around. Tromp tromp tromp.

There's a tunnel here! It's full of glowing fungus; isn't that neat?

Oooh, that is neat! Tromp tromp cave tromp.

If caves could have emotions, this one would be glad she appreciates it. But they can't.

The Diglett and Dugtrio in here are glad to have some new opponents, though!

Hey, buddies! Have some fights, buddies.

She can alternate between fighting in the cave and healing (eating, sleeping) in town for as long as she wants. If and when she gets sick of that, the cave does have another exit. 

Her team would love to fight all week, probably, but she's on a Journey. She will head for the exit sooner rather than later.

She emerges north of Viridian Forest. There are some more small trees it looks possible to cut down, including one that's threatening to block off someone's driveway. It's already been halfheartedly attacked with a saw.

Oh dear, she definitely can't let that last tree stay being in the way. Mushy, cut!

Cutcutcutcut THUMP. 

A man comes out of the little house at the other end of the path. "Oh, are you getting rid of that tree? Much appreciated! I moved here because I like being surrounded by trees, but I didn't need to be shoving past that one every time I went for groceries."

Smile, taptaptap. "It did look like someone wanted it gone."

"Just so. Tell you what, help me and my clefable haul it out of the way and I'll give you an HM for your trouble. Here, Chelsea!" A clefable comes bouncing out of the house.

Nodnod, thumbs up.

Basauw's probably the best for hauling, with his vines and all.

The tree cooperates with being hauled, or at least doesn't actively interfere.

"Here you go! This will teach your Pokemon "flash"!"

Smile, stashing of HM, moving onwards. Also, Basauw gets a pets. Pets pets.

"Ivysaur!"

The packaging for Flash says "great for exploring caves"! Her map says she can get around that Snorlax by going through Rock tunnel, with its entrance on route 10 near Cerulean City.

Well, if she's going through a tunnel again, she might as well see which of her Pokemon can learn Flash.

All of them except Gywa.

Hmmmmm..... Fern shall learn it. And then Gwen will go boldly around that Snorlax via that tunnel.

Fern lights up the tunnel! It's aesthetic in a slightly spooky way. Also full of Zubat.

Pah, Zubat. Here, team, tire out these Zubat so she can get to the end of the tunnel.

You got it, best friend! Those Zubat won't give you any trouble while we're here!

And so they will get to the end of the tunnel without incident. Probably.