A story about a Giant Alien Blob/Mass chasing a space ship

Question

So this space ship lands on this planet and the crew finds a giant portion of forest is just destroyed. They get in the ship and they follow this path, they come to a giant amoeba blob thing absorbing plants and animals. They try to take samples but it attacks them, they get back in the ship but it follows them. It follows them all over the planet.

Answer 1

"The Immeasurable Horror", a short story by Clark Ashton Smith; first published in Weird Tales, September 1931, available at the Internet Archive; reprinted in various places including Avon Science Fiction Reader #1, 1951, also available at the Internet Archive. The full text is available at The Eldritch Dark.

So this space ship lands on this planet

I was with the first Venusian expedition, under the leadership of Admiral Carfax, in 1977. We were able to make no more than a mere landing, and were then compelled to return earthward because of our shortage of oxygen, due to a serious miscalculation regarding our needs. It was unsafe, we found, to breathe the thick, vapor-laden air of Venus for more than short intervals; and we couldn't afford to make an overdraft on our tanks. In 1979 we went back, more fully equipped for all contingencies this time, and landed on a high plateau near the equator. This plateau, being comparatively free from the noxious flora and fauna of the abysmal steaming jungles, was to form the base of our explorations.

I felt signally honored when Admiral Carfax put me in charge of the planetary coaster whose various parts had been brought forth from the bowels of the huge ether-ship and fitted together for local use.

and the crew finds a giant portion of forest is just destroyed.

After we had flown on for an hour or two above the serried jungle, we crossed a great river that couldn't have been so very far below the boiling-point, to judge from the columns of steam that coiled upward from it. Here we could measure the height of the jungle, for the shores were lined with titanic reeds marked off in ten yard segments, that rose for a hundred yards in air, and were overshadowed by the palm-ferns behind them. But even here there was no place for us to descend. We crossed other rivers, some of which would have made the Amazon look like a summer creek; and we must have gone on for another hour above that fuming, everlasting forest ere we came to a clear spot of land.

We wondered about that clearing, even at first sight. It was a winding mile-wide swath in the jungle, whose end and beginning were both lost in the vapors. The purplish soil seemed to have been freshly cleared, and was clean and smooth as if a whole legion of steam-rollers had gone over it. We were immensely excited, thinking that it must be the work of intelligent beings — of whom, so far, we had found no slightest trace.

They get in the ship and they follow this path,

"Harmon, that swath must have been made within the last hour!" exclaimed Manville to me as we climbed back into the vessel behind the others.

"If we follow it," I rejoined, "we'll soon find who, or what, is making it. Are you fellows game for a little side-trip?" I had closed the manhole and was now addressing all four of my companions.

There was no demur from any one, though the following of the swath would mean a diagonal divagation from our set course. All of us were tense with excitement and curiosity. No one could venture a surmise that seemed at all credible, concerning the agency that had left a mile-wide trail. And also we were undecided as to the direction of its progress.

I set the engines running, and with that familiar roar of disintegrating carbon atoms in the cylinders beneath us, we soared to the level of the fern-tops and I steered the coaster in the direction towards which its nose happened to be pointing. However, we soon found that we were on the wrong track; for the new growth below us became disproportionately taller and thicker, as the mighty jungle sought to refill the gap that had been cloven through its center. So I turned the coaster, and we went back in the opposite direction.

they come to a giant amoeba blob thing absorbing plants and animals.

The vapors had closed in before us; now they eddied to each side, leaving the landscape visible for many miles. I think we all saw the Thing simultaneously; but no one spoke for a full thirty seconds. Then Manville muttered, very softly: "My God!"

In front, no more than a half-mile distant, the swath was filled from side to side with a moving mass of livid angleworm pink that rose above the jungle-tops. It was like a sheer cliff before us as we flew toward it. We could see that it was moving away from us, was creeping onward through the forest. The mass gave the impression of a jelly-fish consistency. It rose and fell, expanding and contracting in a slow rhythmic manner, with a noticeable deepening of color at each contraction.

"Life!" murmured Manville, "Life, in an unknown form on a scale that would not be possible in our world."

The coaster was now rushing toward the worm-coloured mass at more than two hundred miles an hour. A moment more, and we would have plunged into that palpitating wall. I turned the wheel sharply, and we veered to the left and rose with an odd sluggishness above the jungle, where we could look down. That sluggishness worried me, after our former headlong speed. It was as if we were fighting some new gravitational force of unexpected potency.

We all had a feeling of actual nausea as we gazed down. There were leagues and leagues of that living substance; and the farther end was lost in the fuming vapors. It was moving faster than a man could run, with that horribly regular expansion and contraction, as if it were breathing. There were no visible limbs or appendages, no organs of any distinguishable kind; but we knew that the thing was alive and aware.

They try to take samples but it attacks them, they get back in the ship but it follows them.

"I guess we might as well go on," observed Manville regretfully. "I'd like to analyze a section of that stuff; but we've seen what it can do; and I can't ask you to take any chances with the coaster."

"No," I agreed, "there's nothing to be done about it. So, if you gentlemen are all willing, we might as well resume our course."

I set the vessel back toward the equator, at a goodly speed.

"Christ! that stuff is following us!" cried Manville a minute later. He had been watching from a rear port.

It follows them all over the planet.

We flew at top speed, but that flowing mass of life — protoplasm, organism, or whatever it was — fairly raced us. At last we got ahead of it, where it slithered in mile-wide devastation through the jungle — but not very far ahead at that. It hung on interminably, and we all grew sick with watching it.

Answer 2

This is "The Immeasurable Horror," by Clark Ashton Smith. The second mission to Venus encounters something that is cutting its way through the rapidly regrowing jungle.

In front, no more than a half-mile distant, the swath was filled from side to side with a moving mass of livid angleworm pink that rose above the jungle-tops. It was like a sheer cliff before us as we flew toward it. We could see that it was moving away from us, was creeping onward through the forest. The mass gave the impression of a jelly-fish consistency. It rose and fell, expanding and contracting in a slow rhythmic manner, with a noticeable deepening of color at each contraction.

After the explorers stop and try to get a look at it, it pursues their rocket plane back toward base camp, and the whole mission is in peril. They only escape when another blob appears, and they eat each other.