this is "nightline." >> tonight, on the bus and behind the scenes with ted cruz as the gloves come off in the race for president. >> he's got this cloud over his head. >> donald trump now taking aim at a serious threat in iowa and new hampshire. >> cruz appealing to the voters 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.

buying has pushed the jackpot to half a billion dollars. what to do if you get lucky tonight.

number 1 in just 60 seconds. good evening. thanks for joining us.

from north korea that it tested a hydrogen bomb. it sent diplomats scrambling, and the u.s. launched planes to verify. but out on the campaign trail it gave candidates a chance to appear 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 nervously. 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 paranoid, isolated nation. they are -- when you have a

you are a threat. >> this underscores the gravity of the threats we are facing right now. >> 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. with 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, enemies 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

you're still emotional. why are you crying? >> because we need such a change in our country. >> reporter: he's on a six-day, 28-stop tour 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 landscape 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

cruz can even be president since he was born in canada to an american mother. trump even suggesting democrats 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 religion. 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

and i'm certainly not going tone gauge in that. i hope donald won't either. >> reporter: if i'm a trump 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 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. we will triple the border 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.

>> reporter: so how is cruz catching up to the trump train? one of the cornerstones of cruz's support here in iowa and 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. 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.

announced he was running for president last more -- >> i believe in the power of 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.

my 5-year-old catherine two days ago woke me up in my hotel room 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.

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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 on "gma" taking us deep inside a glacier, where you can see climate change happening up close. abc's amy robach has the story. >> 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.

>> intimidating standing here looking up. >> reporter: the immense forbidding ice sheets of iceland. home to a hidden world of crystal clear ice caves, glistening glaciers, and dangerous crevices constantly changing. this smugmug documentsts capturing the stunning beauty and treachery of the terrain. we're standing in the middle of thth melting vakna glacier. and scattered all throughout this glacier are massive vertical sinkholes that are treacherous. they go hundreds, even thousands of f ft 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

multiday expedition. 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.

slippery slope. pulling myself up by my own weight, picks on my hands and feet, the ice giving way beneath 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 trekking nearly 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 per 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

and take a look at this. if sea levels keep rising, in two centuries some scientists warn that city could be completely underwater. charleston too. even new york. and these other low-lying areas around the globe, tire 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 debris 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 eventually ending up in the 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 when they get down there and what will we all see?

interesting and least known parts of glacier research which is how does water from the surface get to the base and help lubricate the base to make the 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 s srounded by black and blue ice. and i can tell you one thing. i have a 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."

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finally tonight, $2 and a a dream. so many of us tonight hoping that's all it takes to become a multibajillionaire. tonight's powerball 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.

silly-looking oversizeed check. >> there you go. >> okay. it's crazy. >> 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 sumayment and pocketed a mere 140 million bucks after taxes. >> i was having a really bad night at work, ought, well, i might as well check my numbers while i'm sitting 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 with the winnings? tackle those new year resolutions for starters. if your goal is to get fit, maybe you want to look fabulous like g gneth paltrow or kate hudson hudson.

celeb trainer to the stars tracy anderson at her monthly rate, for you, your family and friends for life. or if you simple ry why want to get out more, tonight's jackpot will get you nearly 25,000 trips 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 losing their riches is only winners. like abraham shakespeare, who won 30 million in florida in 2006, was foundurdered 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. 70% to 80% of powerball jackpot winning tickets have been

but if you insist on picking the 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 to "good morning america" tomorrow and as always