Trama

When Scrat's acorn sends an asteroid to Earth, the Herd must find a way to stop the asteroid from hitting Earth with the help of a returning friend.

Scrat's epic pursuit of his elusive acorn catapults him outside of Earth, where he accidentally sets off a series of cosmic events that transform and threaten the planet. To save themselves from peril, Manny, Sid, Diego, and the rest of the herd leave their home and embark on a quest full of thrills and spills, highs and lows, laughter and adventure while traveling to exotic new lands and encountering a host of colorful new characters.

Scrat is once again trying to bury his acorn but accidentally activates an abandoned alien ship that takes him into deep space, where he unwittingly sends several asteroids en route to a collision with Earth. Meanwhile, Manny and Ellie are preparing upcoming marriage between Peaches and her fiance, Julian. Diego and his wife Shira want to start a family, but their fierce appearance tends to scare kids. Sid is dumped by his girlfriend, Francine, just as he is about to propose to her, and he laments his solitude. During Manny and Ellie's wedding anniversary party, some of the asteroids strike the place and The Herd barely escape. Meanwhile, at the underground lost world, Buck returns a dinosaur egg back to its rightful owner after it was stolen by a trio of flying tyrannosaurs named Gavin, Gertie, and Roger. Buck discovers an ancient stone pillar and takes it to the surface, where he meets Manny and the others..

With Scrat marooned in deep space, triggering an endless string of cosmic events, the mismatched band of prehistoric friends--Manny, the woolly mammoth; his mate, Ellie; Diego, the sabre-toothed tiger, and Sid, the well-meaning sloth--get ready for Peaches' engagement. Now, after the events of L'era glaciale 4 - Continenti alla deriva (2012), only a cataclysmic incident of epic proportions could stop the wedding. However, fate has other plans for them: Manny's secret wish is about to come true. Before long, strange shooting stars reach the Earth's atmosphere. These unprecedented phenomena threaten to wipe out all life forms unless a trusted companion from the past lends a hand with his specialised scientific expertise. This time, things are getting hairy. Will Manny's team cheat death and survive extinction once more?—Nick Riganas

With an asteroid on route to hit Earth, the group must find a way to stop it from hitting the planet and save everyone. With the help of an old friend, the group travel to the last crash site and meet new friends to develop a plan to stop disaster from striking them.—RECB3

Scientists have wondered if the creation of the Universe in its present form is part of a master plan, a series of chance events and something much dumber.

Scrat (Chris Wedge), trying to bury his acorn, accidentally falls through a thin layer of ice and into a large cavern where he finds a spaceship. Scrat activates the abandoned alien ship buried in deep ice, that takes him into deep space. The spaceship hits the moon which in turn pushes all the other planets into their orbits and kick starts the fusion reaction inside the sun. As Scrat grapples with the controls (the acorn was stuck on the master control) he unwittingly sends one large asteroid and associated minor asteroids on route to a collision with Earth.

Meanwhile, Manny (Ray Romano) is worried about the upcoming marriage between Peaches (Keke Palmer) and her fiance, Julian (Adam DeVine). Manny disapproves of Julian, as he finds Julian annoying and incapable of protecting Peaches. Ever since Julian came along, Peaches spends more time with him, than with Manny and he feels neglected.

The concern escalates when Peaches reveals her wish to travel and explore the world as their honeymoon, which both Manny and Ellie (Queen Latifah) oppose. Ellie says that she assumed that Peaches and Julian would stay with them for a while.

Diego (Denis Leary) and his wife Shira (Jennifer Lopez) want to start a family, but their fierce appearance tend to scare kids. Crash (Seann William Scott) and Eddie (Josh Peck) are two possums and Ellie's brothers. Granny (Wanda Sykes) is Sid's grandmother. Sid (John Leguizamo) is dumped by his girlfriend, Francine (Melissa Rauch), just as he is about to propose to her, and he laments his solitude. Sid had planned his whole life including his marriage, his kids and his burial plot along with Francine. Francine says that Sid is crazy as they only had 1 date, and it lasted for 14 minutes. It is the spring season, and everybody has a mate, which makes Sid feel very lonely.

Meanwhile, Scrat is having his own issues inside the spaceship when he turns the gravity way high (57.29 relative to Earth's 1.0) and is pinned to the ground.

Ellie plans a surprise wedding anniversary party for Manny and invites the whole herd to it. Manny is embarrassed as he completely forgot about the anniversary, making Ellie sad. During Manny and Ellie's wedding anniversary party, some of the asteroids explode in the atmosphere, lighting up the sky. Ellie believes that Manny did this on purpose and prepares to forgive him. But then some of the asteroids strike the venue and the herd barely escape with their lives as they take shelter inside a cave. The meteor fragments that hit the surface have a strange purple glow to it.

Meanwhile, at the underground cavern, Buck (Simon Pegg) a one-eyed weasel and a dinosaur hunter, returns a dinosaur egg back to its rightful owner after it was stolen by a trio of Dromaeosaurs named Gavin (Nick Offerman), Gertie (Stephanie Beatriz), and Roger (Max Greenfield). The Dromaeosaurs are angry with Buck and vow revenge. Buck watches the meteors hit the surface. Buck discovers an ancient stone pillar in an underground temple and takes it to the surface, where he meets Manny and the others. Buck says that the meteor shower is the just the beginning of an impending asteroid that is on a collision course with the planet.

Buck explains to the herd that according to the pillar, every 100 million years or so, the world gets a cosmic cleansing. The asteroids had caused two extinctions in the past and with a massive one still incoming, he believes that the only place they could find a clue to stop it is on the site of the impact of the previous ones. According to its engravings, they always fall at the same place which is a nearby volcano. Buck says that the incoming asteroid is huge and even hiding underground is not going to help them this time. Buck reasons that once they get to the volcano they can figure out what is attracting the asteroid and then how to stop it from hitting the planet.

Time to impact is roughly 2 days and 4 hours. However, the three Dromaeosaurs overhear their conversation, and Gavin and Gertie decide to stop them, believing that they could be safe from the impact, as they can fly, thus not only getting their revenge on Buck, but also killing all mammals and securing domination over Earth for their species. Roger is reluctant, but Gavin and Gertie strong-arm him into cooperating.

Manny and Ellie agree to convince Peaches to stay with them by manipulating her and making her believe that it is her idea. As the herd travels to the crash site, they discover that the asteroids pieces from the past crashing have Electro-Magnetic properties. Buck theorizes that if a huge quantity of smaller asteroids should be gathered and launched into orbit, they could attract the main asteroid as well and prevent it from falling on Earth.

Diego encourages Manny to bond with Julian, as Diego feels that Julian is a good boy and Manny need to give him a chance. Meanwhile Ellie tries to overwhelm Peaches with disaster scenarios of raising a family, while roaming the world, without any family support. But Peaches is more than capable of dealing with disasters.

After facing several obstacles and the interference of the Dromaeosaurs (who abduct Granny, but Granny manages to free herself), the herd arrives at "Geotopia", a community of immortal animals formed inside one of the asteroids that had fallen long ago. Sid meets Brooke (Jessie J), a female ground sloth who falls in love with him.

However, Shangri Llama (Jesse Tyler Ferguson), the leader of Geotopia, refuses to cooperate with Buck's plan to send the city's crystals into space in order to prevent the imminent impact, as they are the key to the residents' longevity. The Llama himself claims to be over 400 years old, and the bunny claims to be 326 years old. Sid inadvertently destroys the entire city when he attempts to remove one of the stones to present Brooke with, immediately aging all of the Geotopians to their true ages.

Once Brooke convinces the Geotopians that preventing the asteroid's fall is more important than their lost youth, they and the herd help with Buck's plan, which is to fill up a geyser vent in the volcano with the crystals so that the pressure launches them into space to draw the asteroid away. The Dromaeosaurs attempt to intervene, but Buck convinces Roger that they will not be able to survive the asteroid, and he in turn convinces Gavin and Gertie to help. Buck convinces them to help and that the dinosaurs can live with them in harmony.

After a small meteor hits Gavin, they accidentally drop the last and biggest crystal, but Manny and Julian work together to throw it back into the volcano, causing Julian to earn Manny's approval. The volcano then erupts, sending the magnetic crystal shards to the sky, which sends the oncoming asteroid back into space, away from Earth.

The herd then departs back home, including Sid, who parts ways from Brooke. Just after they leave, an asteroid piece falls inside a hot spring, giving it rejuvenating properties and making the Geotopians and Sid's grandmother, who stayed behind with them, regain their youth.

After the herd returns, Manny reconciles with Julian, Peaches and Julian celebrate their wedding, Diego and Shira become heroes to the kids who were scared of them before, and a rejuvenated Brooke appears during the ceremony to reunite with Sid.

Scrat gets tangled with the Transporter beams inside the spaceship, and he emerges in various configurations with the acorn fused with different parts of his body. Finally, Scrat gets out of the loop, only to flush the acorn out of the space toilet.

Scrat keeps struggling to control the alien ship until it crashes on Mars, destroying all life on the planet, before returning back to his ship and fleeing back to Earth.