this is "nightline." >> tonight, on the bus and behind the scenes with ted cruz as the gloves come off in the race for presisint. head. >> donald trump now taking a at a serious threat in iowa and new hampshire. with prayers -- >> you had me at hello. >> -- and impersonations. >> make sure to hang him high. into the ice. we go deep inside a glacier where the view is stunning. but what we see is sobering. the effects of warmer temps up close. this mammoth glacier in iceland melting at alarming rates. what this means for the ocean beaches here at home. and millions dreaming of millions tonight as the powerball jackpot nears record territory. a last-minute surge of ticket buying has pushed the jackpot to

tonight. but first, the "nightline" 5. number 1 in just 60 seconds. - at healthcare.gov i found affordable, quality coverage. - man: checkups, emergency services, prescriptions... my insurance covers everytying for my family. - narrator: most people who enroll through healthcare.gov qualify for financial help and avoid paying a fee of $695 or more. this is your last chance to enroll. - someone helped me find a high quality plan and financial help to pay for it. - narrator: sign up at healthcare.gov.

good evening. thanks for joining us. we begin with the shocking claim from north korea that it tested a hydrogen bomb. it sent diplomats scrambling,

but out on the campaign trail it gave candidates a chance to apar presidential. when the news broke, we were behind the scenes on a six-day bus tour with one of the gop front-runners, ted cruz. abc's tom llamas has the story. >> reporter: last night an alarming claim from north korea. state television announcing they had successfully tested a hydrogen bomb to protect north korea from warmongers like the u.s. for hours after, the world waited nervousus. but finally, after analyzing the shock waves, the white house calming fears. >> the initial analysis is not consistent with the claims that the regime has made of a successful hydrogen bomb test. >> reporter: today on the campaign trail the candidates weighing in. >> north korea is a paranoidid isolated nation. they are -- when you have a hydrogen bomb, if that's true, you are a threat. >> this underscores the gravity

>> reporter: we spent the day with republican candidate senator ted cruz. >> i thank you. >> reporter: here in iowa where the caucuses are just 26 days away. >> how are you doing? >> reporter: ted cruz has spent a lot of time and resources here. >> welcome to iowa. >> reporter: and the polling is in his favor. trump and cruz are neck and neck. far ahead. th rubio trailing at 14% and carson at 10%. but some republicans worry cruz is too polarizing, too unwilling to compromise with congress, to win the general election. >> how can you be a president and hate the democrats and hate the culture of washington so much and be effective? >> i don't hate the democrats. it's hillary clinton who describes her, quote, enenees as republicans, as half of the country she considers her enemies. >> i'm praying for you. >> thank you very much. >> reporter: his supporters coming out in droves. some even moved to tears when they meet him. >> you got emotional speaking to senator ted cruz. you're still emotional. why are you crying?

in our country. >> reporter: he's on a six-day, 28-stop tou of iowa in an effort to secure every corner of the hawkeye state. >> talk to me about your momentum in iowa. >> we spend a lot of time just one on one asking for the voters' support. people expect to look you in the eyes. there's an old joke in iowa, are you voting for so and so for president? no, no, i couldn't possibly. i've only met him five times. >> reporter: but nationally the lascape is different. trump trumps the competition. cruz is just at 18%. at one campaign stop a cruz supporter wanted answers. >> how are you going to convince independents and democrats to support you when we know the numbers are against us nationwide? >> i think the way we do it is as reagan said in 1980. you paint in bold colors, not pale pastels. >> reporter: getting close to trump in the polls doesn't come easy or without a fight. on television and in newspapers trump questioning if senator cruz can even be president since he was born in canada to an american mother.

would have a field day challenging cruz's presidential eligibility if he gets the nomination. >> how do you run against the democrat, whoever it may be, and you have this hanging over your head if they bring a lawsuit? a lawsuit would take two, three years#-- >> he says he's a naturally born citizen because his mother was u.s. born, a u.s. citizen, and as a result he's a natural-born citizen. >> well, i hope he's right. >> reporter: moments after stepping off his campaign bus this morning, cruz put it to rest. >> the child of a u.s. citizen born abroad is a natural-born citizen. >> reporter: donald trump a couple weeks ago talked about your ethnicity and your retigion. now he's talking about, you know, that you were born in canada. not criticizing it but saying that you could have problems with that. why do you think he's doing that? >> oh, look, i'm not going to try to psychoanalyze donald trump. you know, my view, if others -- >> do you think he sees you as a threat? >> you'd have to ask him that. a lot of folks in the media would love to see donald and me get in a giant food fight. and i'm certainly not going tone gauge in that. i hope donald won't either.

supporter in iowa or anywhere else in the country, why vote for ted cruz? >> well, listen, i think my record is stronger than his. and i think my record is vonger than every other republican candidate running. >> reporter: cruz and trum have certainly played nice so far, even seemed to agree on one of the biggest issues of the campaign season, immigration. what do you do with the 11 million undocumented immigrants in the u.s.? deport them? or they stay here? >> you enforce the law. you deport them. we will secure the borders. we'll build a wall. patrol. we'll increase fourfold the fixed wing and rotary wing aircraft. we will end sanctuary cities. we'll put in place a strongly verified system at the workplace. we will end welfare benefits for those here illegally. we can solve this problem. >> reporter: tonight on cnn trump saying cruz's immigration plan sounds very familiar. >> he said and we will build a wall. so now he's taking my idea for the wall. i'm glad he's taking it. i think it's the right thing to do. >> reporter: so how is cruz catching up to the trump train? one of the cornerstones of

around the country is his faith. >> we need those prayers desperately. >> reporter: cruz is also trying to show voters another side. staying strong with the help of a fitbit. >> do you go up and down steps? that is awesome. >> reporter: and making voters laugh with comedy bits like his impressions. tonight in iowa it was jerry maguire. >> you had me at hello. >> reporter: monday it was clint eastwood. >> make sure to hang him high. >> bye-bye. have fun storming the white house. >> reporter: he also does a mean billy crystal. >> you look marvelous. >> not bad. >> reporter: the 45-year-old republican candidate graduated from princeton, then harvard law, near the top of his class. a champion debater and an actor on stage. skills that helped him deliver his message to washington with a twist. >> i do not like green eggs and ham. i do not like them, sam i am. >> reporter: the night cruz announced he was running for president last more --

millions of courageous conservatives rising up. >> reporter: his cuban immigrant father waited backstage. >> incredible. >> reporter: cruz met his now wife heidi while on the campaign trail for george w. bush's 2000 white house run. married nearly 15 years, they have two young daughters, caroline and catherine. >> it's really been a joy to get out to the states and just meet with thousands and thousands of people who share our values and who are turning out to hear the message of ted cruz. >> reporter: he admits it's hard being away from his family and tries to bring his girls on the road when he can. >> what's it like to be away from your daughters when they're so young? >> it's the hardest part of the campaign. i mean, our girls, caroline is 7, catherine's 5. we try to bring the girls on the road as much as we can. they're coming out. they'll be joining us here in iowa on friday. what they're on the bounce they're bouncing off the walls. they have fun with it. my 5-year-old catherine two days

my ipad ringing that catherine was face-timing me from her ipad. >> is it tough you? don't get that time back. >> you miss a lot of moments in their lives. but as you noted, that's also why you're doing it. i couldn't look my daughters in the eyes, if i had the ability to do something to stop it, to bring america back and i didn't stand up and lead. so that's a very big part of why i'm doing this. >> a shining city on a hill. >> reporter: tonight cruz working late into the evening, making his case and trying to convince republican voters to put their faith in him. [ applause ] for "nightline" tom llamas in storm lake, iowa. next, an up-close look at the impact of global warming from deep inside a glacier. and later, the huge powerball jackpot that has so many americans hoping to wake up millionaires. to severe crohn's disease is tough, but i've managed. except that managing my symptoms was all i was doing. and when i finally told my doctor, he said humira

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you know, when you think of the word "breathtaking," the location of our next story comes to mind. iceland. the land of fire and ice. but the ice there is melting faster than ever. it's a massive undertaking live >> oh, my gosh. >> reporter: we brought you fire. we're just getting inside that crater. the first ever live drone camera over an active volcano. now we're bringing you ice. >> intimidating standing here looking up. >> reporter: the immense

home to a hidden world of crystal clear ice caves, glistening glaciers, and dangerous crevices constantly changing. this smugmug documentsry capturing the stunning beauty and treachery of the terrain. we're standing in the middle of the melting vakna glacier. and scattered all throughout this glacier are massive vertical sinkholes that are treacherous. they go hundreds, even thousands of feet into the earth, where ice is melting faster and faster as water levels in the atlantic rise even more. >> throughout geelogic time and certainly for the last 2 million years, we've gone through ice ages and warm periods, and glaciers come and go over time. what we're seeing right now, though-s a real rapid increase in the rate of thinning and melting that we're seeing. and that's related to human-induced climate change. >> reporter: gearing up for this treacherous journey has been a

just call these guys glacial life savers. they are an elite unit comprised of volunteers. experienced ice climbers. and true masters of this forbidding terrain. they train on icescapes like this. then descend into the depths of the coldest climates, braving perilous weather conditions to reach people trapped in the most intimidating of landscapes. guides on the ice, they've canceled hollywood too. keeping crews safe on blockbusters from "star wars" to "interstellar" and "game of thrones." we joined them right in the heart of this icy wonderland. >> walk up that wall of ice. and it's perfectly safe? >> yeah. >> you hesitated. >> reporter: ready to lock and load. it's my turn to attack the slippery slope. pulling myself up by my own weight, picks on my hands and

me. getting a small taste of how difficult, dangerous, and exhilarating it all is. and finally -- >> i got up. whoo! >> reporter: then by car and foot our team trekkg n nrly a mile through water, rocks, and ice, all in arctic temperatures. the landscape, dazzling. dangerous. and disappearing fast. losing an average of 11 billion tons of ice p p year. this satellite picture taken in 1986 and this one 28 years later. iceland is melting, and that water has to go somewhere. >> when you're talking about changing sea level, you're talking about impacting the tremendous population around the world. >> reporter: including miami's coastline. those waters already climbing an inch a year. and take a look at thihi if sea levels keep rising, in two centuries some scientists

completely underwater. charleston too. even new york. and these other low-lying areas around the globe, entire ways of life now threatened. so we're plunging far below the surface of the ice in a event. >> hey, guys. go for it. go ahead and start ice climbing. >> reporter: going deep into this glacier. passing bands of darker ice like the rings of a trees showing ash and d bris from volcanic eruptions from ages past. vakna, a glacial sinkhole, a massive pipe for melting ice that can be thousands of feet deep. and all this melting ice ocean. >> this is remarkable watching them scale this massive ice wall. it takes tremendous skill, but it's all to get to the bottom. what do you expect they'll see what will we all see? >> this is one of the most interesting and least known parts of glacier research which

surface get to the base and help lubricate the base to make th glacier flow faster? >> reporter: it's a long treacherous way down but finally - >> guys, i want to check in with you. this is amy again pu made it to the bottom? >> that's right. >> tell me what you're seeing. describe what you're looking at. >> everything is awesome. >> he went ahead with -- >> i'm surrounded by black and blue ice. and i can tell you one thing. i have challenging climb in front of me. >> reporter: but some scientists say not nearly as challenging as the problem we face slowing the per being of this vital hidden world. amy robach in iceland. up next what you could do if you win the massive powerball jackpot. just how many trips around the world could you afford? >> announcer: abc news "nightline." brought to you by viagra. there's something in the air. but here's the thing:

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finally tonight, $2 and a dream. so many of us tonight hoping that's all it takeso become a multibajillionaire. tonight's powerballl jackpot is half a billion dollars. the biggest one in more than two years. here's abc's kayna whitworth. >> reporter: luck be a powerball tonight. just how nice an extra $529 million bucks could be. >> 47, 2, 63, 62, 11. >> reporter: tonight's winning numbers and 17 is the powerball. the cash payout worth a minimum of $306 million in cold hard cash. even though it comes on a silly-looking oversizeed check. >> there you go. >> okay.

>> reporter: just like the one julie weeks from michigan received when she won the powerball jackpot last november. for 23 years she worked at a fiberglass factory. >> are you leaving your job? >> oh, i quit automatically. i was done. >> reporter: that jackpot was worth just over $310 million. but the former factory worker opted for the lump sum payment and pocketed a mere 140 million bucksfter taxes. >> i was having a really bad night at work, thought, well, i might as well check my numbers while i'm sitng here waiting for my lunch. and that's when i realized that i was the winner. i didn't believe it. >> reporter: so what do you do th the winnings? tackle those new year resolutions for starters. if your goal is to get fit, maybe you want to look fabulous like gwyneth paltrow or kate hudson hudson. with $500 million you can hire celeb trainer to the stars tracy anderson at her monthly rate, for you, your family and friends for life.

get out more, tonight's jackpot will get you nearly 25,000 t tps around the world. sky's the limit, but financial experts say keep your purse strings tight by waiting six months or longer before buying anything. according to a 2015 study, 44% of winners spent their entire winnings within five years. and losi their riches is only one bad outcome for lottery winners. like abraham shakespeare, who won 30 million in florida in 2006, was found murdered three years later. a woman who had befriended him is currently serving a life sentence. but if tonight's drawing left you empty-handed, there is a next time. and a fine art to choosing the right numbers. don't pick numbers based on your kids' birthdays or your wedding anniversary. in fact, don't pick the numbers at all. % to 80% of powerball jackpot winning ticke have been computer picked.

numbers, try these -- 8, 54, 14, 39, 13. those are among the most frequently drawn numbers in the past four years. if no one wins the big pot tonight, the next drawing is saturday, when the grand prize is estimated to be worth $675 million, the largest jackpot ever. for "nightline" kayna whitworth, abc news, new york. >> of course if you win you could tweeted me @jujuchangabc because i have a few other ideas on how you can spend that money. thanks for watching abc news. "world news now" is coming up soon with overnight breaking news. tune in t "good morning america" tomorrow and as always

good night, america. >> calvin: a show of support for a fellow officer accused of shooting a man holding an unloaded air rifle. >> the man said he had no

andrew perez is live in fort